Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
def sol():
    n,m=map(int,input().split())
    t,w={},{}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        t[(l,r)]=d
        if l in w:
            w[l].add((r,d))
        else:
            w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    #chk=set()
    chk=deque()
    if len(s)==0:
        print(["No","Yes"][m==0])
        exit()
    for i in s:
        #chk.add((i,0))
        chk.append((i,0))
        while len(chk):
            x=chk.pop()
            if x[0] in w:
                for j in w[x[0]]:
                    if (i,j[0]) in t and t[(i,j[0])]!=x[1]+j[1]:
                    #if (x[0],j[0]) in t and t[(i,j[0])]!=
                        print("No")
                        exit()
                    elif (i,j[0]) not in t:
                        t[(i,j[0])]=x[1]+j[1]
                        #chk.add((j[0],x[1]+j[1]))
                        chk.append((j[0],x[1]+j[1]))
                    else:
                        #chk.add((j[0],x[1]+j[1]))
                        chk.append((j[0],x[1]+j[1]))
    print("Yes")

if __name__=="__main__":
    sol()


Fixed submission:
def sol():
    n,m=map(int,input().split())
    t,w={},{}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w: w[l].add((r,d))
        else: w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    chk=set()
    if len(s)==0:
        print(["No","Yes"][m==0])
        exit()
    for i in s:
        chk.add((i,0))
        while len(chk):
            x=chk.pop()
            if x[0] in w:
                for j in w[x[0]]:
                    if (i,j[0]) in t and t[(i,j[0])]!=t[(i,x[0])]+j[1]:
                        print("No")
                        exit()
                    elif (i,j[0]) not in t:
                        #t[(i,j[0])]=t[(i,x[0])]+j[1]
                        t[(i,j[0])]=x[1]+j[1]
                        chk.add((j[0],x[1]+j[1]))
    print("Yes")

if __name__=="__main__":
    sol()

Buggy python submission (verdict: Time Limit Exceeded):
def sol():
    n,m=map(int,input().split())
    t={}
    w={}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        t[(l,r)]=d
        if l in w:
            w[l].add((r,d))
        else:
            w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    chk=set()
    if len(s)==0:
        print(["No","Yes"][m==0])
        exit()
    for i in s:
        chk.add((i,0))
        while len(chk):
            x=chk.pop()
            if x[0] in w:
                for j in w[x[0]]:
                    if (i,j[0]) in t and t[(i,j[0])]!=x[1]+j[1]:
                    #if (x[0],j[0]) in t and t[(i,j[0])]!=
                        print("No")
                        exit()
                    elif (i,j[0]) not in t:
                        t[(i,j[0])]=x[1]+j[1]
                        chk.add((j[0],x[1]+j[1]))
                    else:
                        chk.add((j[0],x[1]+j[1]))
    print("Yes")

if __name__=="__main__":
    sol()

Fixed submission:
def sol():
    n,m=map(int,input().split())
    t,w={},{}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w: w[l].add((r,d))
        else: w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    chk=set()
    if len(s)==0:
        print(["No","Yes"][m==0])
        exit()
    for i in s:
        chk.add((i,0))
        while len(chk):
            x=chk.pop()
            if x[0] in w:
                for j in w[x[0]]:
                    if (i,j[0]) in t and t[(i,j[0])]!=t[(i,x[0])]+j[1]:
                        print("No")
                        exit()
                    elif (i,j[0]) not in t:
                        #t[(i,j[0])]=t[(i,x[0])]+j[1]
                        t[(i,j[0])]=x[1]+j[1]
                        chk.add((j[0],x[1]+j[1]))
    print("Yes")

if __name__=="__main__":
    sol()

Buggy python submission (verdict: Time Limit Exceeded):
n,m=map(int,input().split())
t={}
w={}
p,q=set(),set()
for i in range(m):
    l,r,d=[int(i) for i in input().split()]
    t[(l,r)]=d
    if l in w:
        w[l].add((r,d))
    else:
        w[l]={(r,d)}
    p.add(l)
    q.add(r)
s=p-q
chk=set()
if len(s)==0:
    print(["No","Yes"][m==0])
    exit()
for i in s:
    chk.add((i,0))
    while len(chk):
        x=chk.pop()
        if x[0] in w:
            for j in w[x[0]]:
                if (i,j[0]) in t and t[(i,j[0])]!=x[1]+j[1]:
                #if (x[0],j[0]) in t and t[(i,j[0])]!=
                    print("No")
                    exit()
                elif (i,j[0]) not in t:
                    t[(i,j[0])]=x[1]+j[1]
                    chk.add((j[0],x[1]+j[1]))
                else:
                    chk.add((j[0],x[1]+j[1]))
print("Yes")

Fixed submission:
def sol():
    n,m=map(int,input().split())
    t,w={},{}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w: w[l].add((r,d))
        else: w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    chk=set()
    if len(s)==0:
        print(["No","Yes"][m==0])
        exit()
    for i in s:
        chk.add((i,0))
        while len(chk):
            x=chk.pop()
            if x[0] in w:
                for j in w[x[0]]:
                    if (i,j[0]) in t and t[(i,j[0])]!=t[(i,x[0])]+j[1]:
                        print("No")
                        exit()
                    elif (i,j[0]) not in t:
                        #t[(i,j[0])]=t[(i,x[0])]+j[1]
                        t[(i,j[0])]=x[1]+j[1]
                        chk.add((j[0],x[1]+j[1]))
    print("Yes")

if __name__=="__main__":
    sol()

Buggy python submission (verdict: Runtime Error):
def sol():
    n,m=map(int,input().split())
    w={}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w:
            w[l].add((r,d))
        else:
            w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    for i in s:
        k={j for j in w[i]}
        g=set()
        cnt=0
        while len(k):
            x=k.pop()
            cnt+=1
            if cnt==121212:
                print(p[10])
                exit()
                
            if x[0] not in w:
                g.add(x)
            else:
                for j in w[x[0]]:
                    k.add((j[0],j[1]+x[1]))
        y=set()
        for j in g:
            if j[0] in y or j[0]==i:
                print("No")
                exit()
            else:
                y.add(j[0]) 
    print("Yes" if len(s) or m==0 else "No")

if __name__=="__main__":
    sol()

Fixed submission:
def sol():
    n,m=map(int,input().split())
    t,w={},{}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w: w[l].add((r,d))
        else: w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    chk=set()
    if len(s)==0:
        print(["No","Yes"][m==0])
        exit()
    for i in s:
        chk.add((i,0))
        while len(chk):
            x=chk.pop()
            if x[0] in w:
                for j in w[x[0]]:
                    if (i,j[0]) in t and t[(i,j[0])]!=t[(i,x[0])]+j[1]:
                        print("No")
                        exit()
                    elif (i,j[0]) not in t:
                        #t[(i,j[0])]=t[(i,x[0])]+j[1]
                        t[(i,j[0])]=x[1]+j[1]
                        chk.add((j[0],x[1]+j[1]))
    print("Yes")

if __name__=="__main__":
    sol()

Buggy python submission (verdict: Runtime Error):
def sol():
    n,m=map(int,input().split())
    w={}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w:
            w[l].add((r,d))
        else:
            w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    for i in s:
        k={j for j in w[i]}
        g=set()
        cnt=0
        while len(k):
            x=k.pop()
            cnt+=1
            if cnt==5000:
                print(p[100])
            if x[0] not in w:
                g.add(x)
            else:
                for j in w[x[0]]:
                    k.add((j[0],j[1]+x[1]))
        y=set()
        for j in g:
            if j[0] in y or j[0]==i:
                print("No")
                exit()
            else:
                y.add(j[0])
    print("Yes" if len(s) or m==0 else "No")

if __name__=="__main__":
    sol()

Fixed submission:
def sol():
    n,m=map(int,input().split())
    t,w={},{}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w: w[l].add((r,d))
        else: w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    chk=set()
    if len(s)==0:
        print(["No","Yes"][m==0])
        exit()
    for i in s:
        chk.add((i,0))
        while len(chk):
            x=chk.pop()
            if x[0] in w:
                for j in w[x[0]]:
                    if (i,j[0]) in t and t[(i,j[0])]!=t[(i,x[0])]+j[1]:
                        print("No")
                        exit()
                    elif (i,j[0]) not in t:
                        #t[(i,j[0])]=t[(i,x[0])]+j[1]
                        t[(i,j[0])]=x[1]+j[1]
                        chk.add((j[0],x[1]+j[1]))
    print("Yes")

if __name__=="__main__":
    sol()

Buggy python submission (verdict: Runtime Error):
def sol():
    n,m=map(int,input().split())
    w={}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w:
            w[l].add((r,d))
        else:
            w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    for i in s:
        k={j for j in w[i]}
        g=set()
        cnt=0
        while len(k):
            x=k.pop()
            cnt+=1
            if cnt==1000:
                print(p[100])
            if x[0] not in w:
                g.add(x)
            else:
                for j in w[x[0]]:
                    k.add((j[0],j[1]+x[1]))
        y=set()
        for j in g:
            if j[0] in y or j[0]==i:
                print("No")
                exit()
            else:
                y.add(j[0])
    print("Yes" if len(s) or m==0 else "No")

if __name__=="__main__":
    sol()

Fixed submission:
def sol():
    n,m=map(int,input().split())
    t,w={},{}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w: w[l].add((r,d))
        else: w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    chk=set()
    if len(s)==0:
        print(["No","Yes"][m==0])
        exit()
    for i in s:
        chk.add((i,0))
        while len(chk):
            x=chk.pop()
            if x[0] in w:
                for j in w[x[0]]:
                    if (i,j[0]) in t and t[(i,j[0])]!=t[(i,x[0])]+j[1]:
                        print("No")
                        exit()
                    elif (i,j[0]) not in t:
                        #t[(i,j[0])]=t[(i,x[0])]+j[1]
                        t[(i,j[0])]=x[1]+j[1]
                        chk.add((j[0],x[1]+j[1]))
    print("Yes")

if __name__=="__main__":
    sol()

Buggy python submission (verdict: Runtime Error):
def sol():
    n,m=map(int,input().split())
    w={}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w:
            w[l].add((r,d))
        else:
            w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    for i in s:
        k={j for j in w[i]}
        g=set()
        cnt=0
        while len(k):
            x=k.pop()
            cnt+=1
            if cnt==100:
                print(p[100])
            if x[0] not in w:
                g.add(x)
            else:
                for j in w[x[0]]:
                    k.add((j[0],j[1]+x[1]))
        y=set()
        for j in g:
            if j[0] in y or j[0]==i:
                print("No")
                exit()
            else:
                y.add(j[0])
    print("Yes" if len(s) or m==0 else "No")

if __name__=="__main__":
    sol()


Fixed submission:
def sol():
    n,m=map(int,input().split())
    t,w={},{}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w: w[l].add((r,d))
        else: w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    chk=set()
    if len(s)==0:
        print(["No","Yes"][m==0])
        exit()
    for i in s:
        chk.add((i,0))
        while len(chk):
            x=chk.pop()
            if x[0] in w:
                for j in w[x[0]]:
                    if (i,j[0]) in t and t[(i,j[0])]!=t[(i,x[0])]+j[1]:
                        print("No")
                        exit()
                    elif (i,j[0]) not in t:
                        #t[(i,j[0])]=t[(i,x[0])]+j[1]
                        t[(i,j[0])]=x[1]+j[1]
                        chk.add((j[0],x[1]+j[1]))
    print("Yes")

if __name__=="__main__":
    sol()

Buggy python submission (verdict: Runtime Error):
n,m=map(int,input().split())
w={}
#t={}
p,q=set(),set()
for i in range(m):
    l,r,d=[int(i) for i in input().split()]
    if l in w:
        w[l].add((r,d))
    else:
        w[l]={(r,d)}
    #t[(l,r)]=d
    p.add(l)
    q.add(r)

#print(w)
#print(t)
s=p-q
#print(s)
for i in s:
    k={j for j in w[i]}
    g=set()
    while len(k):
        x=k.pop()
        if x[0] not in w:
            g.add(x)
        else:
            for j in w[x[0]]:
                k.add((j[0],j[1]+x[1]))
    y=set()
    for j in g:
        if g[0] in y or g[0]==i:
            print("No")
            exit()
        else:
            y.add(g[0])
print("Yes")

Fixed submission:
def sol():
    n,m=map(int,input().split())
    t,w={},{}
    p,q=set(),set()
    for i in range(m):
        l,r,d=[int(i) for i in input().split()]
        if l in w: w[l].add((r,d))
        else: w[l]={(r,d)}
        p.add(l)
        q.add(r)
    s=p-q
    chk=set()
    if len(s)==0:
        print(["No","Yes"][m==0])
        exit()
    for i in s:
        chk.add((i,0))
        while len(chk):
            x=chk.pop()
            if x[0] in w:
                for j in w[x[0]]:
                    if (i,j[0]) in t and t[(i,j[0])]!=t[(i,x[0])]+j[1]:
                        print("No")
                        exit()
                    elif (i,j[0]) not in t:
                        #t[(i,j[0])]=t[(i,x[0])]+j[1]
                        t[(i,j[0])]=x[1]+j[1]
                        chk.add((j[0],x[1]+j[1]))
    print("Yes")

if __name__=="__main__":
    sol()