Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return

    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
    val = [inf] * N
    global_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        return False
                val[next_v] = val[v] + d
                visited.add(next_v)
                global_visited.add(next_v)
                q.append(next_v)
        return True

    can = True
    for i in range(N):
        if i in global_visited:
            continue
        v = i
        val[v] = 0
        if not bfs(v):
            can = False

    if can:
        print("Yes")
    else:
        print("No")
    return


main()




Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return

    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
    val = [inf] * N
    global_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        return False
                val[next_v] = val[v] + d
                visited.add(next_v)
                global_visited.add(next_v)
                q.append(next_v)
        return True

    can = True
    for i in range(N):
        if i in global_visited:
            continue
        v = i
        val[v] = 0
        if not bfs(v):
            can = False
            break

    if can:
        print("Yes")
    else:
        print("No")
    return


main()

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return
    uf = UnionFind(N)
    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))

    val = [inf] * N
    glb_visited = set()

    def bfs(ini):
        q = deque([ini])
        visited = set()
        visited.add(ini)
        glb_visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        return False
                val[next_v] = val[v] + d
                visited.add(next_v)
                glb_visited.add(next_v)
                q.append(next_v)
        return True

    can = True

    for k in range(N):
        if k in glb_visited:
            continue
        val[k] = 0
        if not bfs(k):
            can = False

    if can:
        print("Yes")
    else:
        print("No")
    return

main()



Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return

    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
    val = [inf] * N
    global_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        return False
                val[next_v] = val[v] + d
                visited.add(next_v)
                global_visited.add(next_v)
                q.append(next_v)
        return True

    can = True
    for i in range(N):
        if i in global_visited:
            continue
        v = i
        val[v] = 0
        if not bfs(v):
            can = False
            break

    if can:
        print("Yes")
    else:
        print("No")
    return


main()

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return
    uf = UnionFind(N)
    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
        uf.union(l, r)
        uf.find(r)

    val = [inf] * N
    glb_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        glb_visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        flag = False
                        break
                val[next_v] = val[v] + d
                visited.add(next_v)
                glb_visited.add(next_v)
                q.append(next_v)
        if flag:
            return True
        return False

    can = True

    for k in range(N):
        if k in glb_visited:
            continue
        val[k] = 0
        if not bfs(k):
            can = False

    if can:
        print("Yes")
    else:
        print("No")
    return

main()



Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return

    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
    val = [inf] * N
    global_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        return False
                val[next_v] = val[v] + d
                visited.add(next_v)
                global_visited.add(next_v)
                q.append(next_v)
        return True

    can = True
    for i in range(N):
        if i in global_visited:
            continue
        v = i
        val[v] = 0
        if not bfs(v):
            can = False
            break

    if can:
        print("Yes")
    else:
        print("No")
    return


main()

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return
    uf = UnionFind(N)
    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
        uf.union(l, r)
        uf.find(r)

    val = [inf] * N

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        flag = False
                        break
                val[next_v] = val[v] + d
                visited.add(next_v)
                q.append(next_v)
        if flag:
            return True
        return False

    can = True

    for k, v in uf.all_group_members().items():
        val[k] = 0
        if not bfs(k):
            can = False

    if can:
        print("Yes")
    else:
        print("No")
    return

main()



Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return

    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
    val = [inf] * N
    global_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        return False
                val[next_v] = val[v] + d
                visited.add(next_v)
                global_visited.add(next_v)
                q.append(next_v)
        return True

    can = True
    for i in range(N):
        if i in global_visited:
            continue
        v = i
        val[v] = 0
        if not bfs(v):
            can = False
            break

    if can:
        print("Yes")
    else:
        print("No")
    return


main()

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return
    uf = UnionFind(N)
    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
        uf.union(l, r)

    val = [inf] * N

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        flag = False
                        break
                val[next_v] = val[v] + d
                visited.add(next_v)
                q.append(next_v)
        if flag:
            return True
        return False

    can = True

    for k, v in uf.all_group_members().items():
        val[k] = 0
        if not bfs(k):
            can = False

    if can:
        print("Yes")
    else:
        print("No")
    return

main()



Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return

    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
    val = [inf] * N
    global_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        return False
                val[next_v] = val[v] + d
                visited.add(next_v)
                global_visited.add(next_v)
                q.append(next_v)
        return True

    can = True
    for i in range(N):
        if i in global_visited:
            continue
        v = i
        val[v] = 0
        if not bfs(v):
            can = False
            break

    if can:
        print("Yes")
    else:
        print("No")
    return


main()

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return

    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
    val = [inf] * N
    global_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        global_visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        flag = False
                        break
                val[next_v] = val[v] + d
                visited.add(next_v)
                global_visited.add(next_v)
                q.append(next_v)
        if flag:
            return True
        return False

    can = True
    for i in range(N):
        if i in global_visited:
            continue
        v = i
        val[v] = 0
        if not bfs(v):
            can = False

    if can:
        print("Yes")
    else:
        print("No")
    return




main()



Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return

    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
    val = [inf] * N
    global_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        return False
                val[next_v] = val[v] + d
                visited.add(next_v)
                global_visited.add(next_v)
                q.append(next_v)
        return True

    can = True
    for i in range(N):
        if i in global_visited:
            continue
        v = i
        val[v] = 0
        if not bfs(v):
            can = False
            break

    if can:
        print("Yes")
    else:
        print("No")
    return


main()

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return

    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
    val = [inf] * N
    global_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        flag = False
                        break
                val[next_v] = val[v] + d
                visited.add(next_v)
                global_visited.add(next_v)
                q.append(next_v)
        if flag:
            return True
        return False

    can = True
    for i in range(N):
        if i in global_visited:
            continue
        v = i
        val[v] = 0
        if not bfs(v):
            can = False

    if can:
        print("Yes")
    else:
        print("No")
    return




main()



Fixed submission:
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time,copy,functools
from collections import deque

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

DR = [1, -1, 0, 0]
DC = [0, 0, 1, -1]

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
     

def main():
    N, M = LI()
    if M == 0:
        print("Yes")
        return

    G = [[] for _ in range(N)]
    for i in range(M):
        l, r, d = LI()
        l -= 1
        r -= 1
        G[l].append((r, d))
        G[r].append((l, -d))
    val = [inf] * N
    global_visited = set()

    def bfs(ini):
        flag = True
        q = deque([ini])
        visited = set()
        visited.add(ini)
        while q:
            v = q.popleft()
            for next_v, d in G[v]:
                if next_v in visited:
                    if val[next_v] == val[v] + d:
                        continue
                    else:
                        return False
                val[next_v] = val[v] + d
                visited.add(next_v)
                global_visited.add(next_v)
                q.append(next_v)
        return True

    can = True
    for i in range(N):
        if i in global_visited:
            continue
        v = i
        val[v] = 0
        if not bfs(v):
            can = False
            break

    if can:
        print("Yes")
    else:
        print("No")
    return


main()