Buggy python submission (verdict: Runtime Error):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

def main():
	N = INT()
	ab = [LIST() for _ in range(N-1)]

	graph = defaultdict(list)

	# edge = [[0]*N for _ in range(N)]
	edge = defaultdict(int)
	for a, b in ab:
		graph[a-1].append(b-1)
		graph[b-1].append(a-1)

	K = 0
	for v in graph.values():
		K = max(K, len(v))
	color = list(range(1, K+1))

	def DFS(i, color_from):  # color_fromからきた色を使わない
		tmp = -1
		for node in graph[i]:
			str_ = f"{i},{node}"
			if not edge[str_]:
				use_color = color[tmp]
				if use_color == color_from:
					use_color = color[tmp-1]
					tmp -= 1
				tmp -= 1
				edge[str_] = use_color
				edge[f"{node},{i}"] = use_color
				DFS(node, use_color)

	DFS(0, None)

	print(K)
	for a, b in ab:
		print(edge[f"{a-1},{b-1}"])


if __name__ == "__main__":
	main()


Fixed submission:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

def main():
	N = INT()
	ab = [LIST() for _ in range(N-1)]

	graph = defaultdict(list)

	# edge = [[0]*N for _ in range(N)]
	edge = defaultdict(int)
	for a, b in ab:
		graph[a-1].append(b-1)
		graph[b-1].append(a-1)

	K = 0
	for v in graph.values():
		K = max(K, len(v))
	color = list(range(1, K+1))

	q = deque()
	q.append((0, None))

	while q:
		i, color_from = q.popleft()
		tmp = -1
		for node in graph[i]:
			str_ = "{},{}".format(i, node)
			if not edge[str_]:
				use_color = color[tmp]
				if use_color == color_from:
					use_color = color[tmp-1]
					tmp -= 1
				tmp -= 1
				edge[str_] = use_color
				edge["{},{}".format(node, i)] = use_color
				q.append((node, use_color))
	print(K)
	for a, b in ab:
		print(edge["{},{}".format(a-1, b-1)])


if __name__ == "__main__":
	main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

N = INT()
ab = [LIST() for _ in range(N-1)]

graph = defaultdict(list)

edge = [[0]*N for _ in range(N)]
for a, b in ab:
	graph[a-1].append(b-1)
	graph[b-1].append(a-1)

K = 0
for i in graph:
	K = max(K, len(graph[i]))
color = list(range(1, K+1))

def DFS(i, color_from):  # color_fromからきた色を使わない
	tmp = -1
	for node in graph[i]:	
		if not edge[i][node]:
			use_color = color[tmp]
			if use_color == color_from:
				use_color = color[tmp-1]
				tmp -= 1
			tmp -= 1
			edge[i][node] = use_color
			edge[node][i] = use_color
			DFS(node, use_color)

DFS(0, None)

print(K)
for a, b in ab:
	print(edge[a-1][b-1])


Fixed submission:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

def main():
	N = INT()
	ab = [LIST() for _ in range(N-1)]

	graph = defaultdict(list)

	# edge = [[0]*N for _ in range(N)]
	edge = defaultdict(int)
	for a, b in ab:
		graph[a-1].append(b-1)
		graph[b-1].append(a-1)

	K = 0
	for v in graph.values():
		K = max(K, len(v))
	color = list(range(1, K+1))

	q = deque()
	q.append((0, None))

	while q:
		i, color_from = q.popleft()
		tmp = -1
		for node in graph[i]:
			str_ = "{},{}".format(i, node)
			if not edge[str_]:
				use_color = color[tmp]
				if use_color == color_from:
					use_color = color[tmp-1]
					tmp -= 1
				tmp -= 1
				edge[str_] = use_color
				edge["{},{}".format(node, i)] = use_color
				q.append((node, use_color))
	print(K)
	for a, b in ab:
		print(edge["{},{}".format(a-1, b-1)])


if __name__ == "__main__":
	main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

N = INT()
ab = [LIST() for _ in range(N-1)]

graph = defaultdict(list)

edge = [[0]*N for _ in range(N)]
for a, b in ab:
	graph[a-1].append(b-1)
	graph[b-1].append(a-1)

K = 0
for i in graph:
	K = max(K, len(graph[i]))
color = list(range(1, K+1))

def DFS(i, color_from):  # color_fromからきた色を使わない
	can_use_color = color[:]
	for node in graph[i]:
		if not edge[i][node]:
			use_color = can_use_color.pop()
			if use_color == color_from:
				use_color = can_use_color.pop()
			edge[i][node] = use_color
			edge[node][i] = use_color
			DFS(node, use_color)

DFS(0, None)

print(K)
for a, b in ab:
	print(edge[a-1][b-1])


Fixed submission:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

def main():
	N = INT()
	ab = [LIST() for _ in range(N-1)]

	graph = defaultdict(list)

	# edge = [[0]*N for _ in range(N)]
	edge = defaultdict(int)
	for a, b in ab:
		graph[a-1].append(b-1)
		graph[b-1].append(a-1)

	K = 0
	for v in graph.values():
		K = max(K, len(v))
	color = list(range(1, K+1))

	q = deque()
	q.append((0, None))

	while q:
		i, color_from = q.popleft()
		tmp = -1
		for node in graph[i]:
			str_ = "{},{}".format(i, node)
			if not edge[str_]:
				use_color = color[tmp]
				if use_color == color_from:
					use_color = color[tmp-1]
					tmp -= 1
				tmp -= 1
				edge[str_] = use_color
				edge["{},{}".format(node, i)] = use_color
				q.append((node, use_color))
	print(K)
	for a, b in ab:
		print(edge["{},{}".format(a-1, b-1)])


if __name__ == "__main__":
	main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

N = INT()
ab = [LIST() for _ in range(N-1)]

graph = defaultdict(list)

edge = [[0]*N for _ in range(N)]
for a, b in ab:
	graph[a-1].append(b-1)
	graph[b-1].append(a-1)

K = 0
for i in graph:
	K = max(K, len(graph[i]))
color = list(range(1, K+1))
def DFS(i, color_from):  # color_fromからきた色を使わない
	can_use_color = color.copy()
	for node in graph[i]:
		if not edge[i][node]:
			use_color = can_use_color.pop()
			if use_color == color_from:
				use_color = can_use_color.pop()
			edge[i][node] = use_color
			edge[node][i] = use_color
			DFS(node, use_color)

DFS(0, None)

print(K)
for a, b in ab:
	print(edge[a-1][b-1])


Fixed submission:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

def main():
	N = INT()
	ab = [LIST() for _ in range(N-1)]

	graph = defaultdict(list)

	# edge = [[0]*N for _ in range(N)]
	edge = defaultdict(int)
	for a, b in ab:
		graph[a-1].append(b-1)
		graph[b-1].append(a-1)

	K = 0
	for v in graph.values():
		K = max(K, len(v))
	color = list(range(1, K+1))

	q = deque()
	q.append((0, None))

	while q:
		i, color_from = q.popleft()
		tmp = -1
		for node in graph[i]:
			str_ = "{},{}".format(i, node)
			if not edge[str_]:
				use_color = color[tmp]
				if use_color == color_from:
					use_color = color[tmp-1]
					tmp -= 1
				tmp -= 1
				edge[str_] = use_color
				edge["{},{}".format(node, i)] = use_color
				q.append((node, use_color))
	print(K)
	for a, b in ab:
		print(edge["{},{}".format(a-1, b-1)])


if __name__ == "__main__":
	main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

N = INT()
ab = [LIST() for _ in range(N-1)]

graph = defaultdict(list)

edge = [[0]*N for _ in range(N)]
for a, b in ab:
	graph[a-1].append(b-1)
	graph[b-1].append(a-1)

K = 0
for i in graph:
	K = max(K, len(graph[i]))

def DFS(i, color_from):  # color_fromからきた色を使わない
	can_use_color = list(range(1, K+1))
	for node in graph[i]:
		if not edge[i][node]:
			use_color = can_use_color.pop()
			if use_color == color_from:
				use_color = can_use_color.pop()
			edge[i][node] = use_color
			edge[node][i] = use_color
			DFS(node, use_color)

DFS(0, None)

print(K)
for a, b in ab:
	print(edge[a-1][b-1])


Fixed submission:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

def main():
	N = INT()
	ab = [LIST() for _ in range(N-1)]

	graph = defaultdict(list)

	# edge = [[0]*N for _ in range(N)]
	edge = defaultdict(int)
	for a, b in ab:
		graph[a-1].append(b-1)
		graph[b-1].append(a-1)

	K = 0
	for v in graph.values():
		K = max(K, len(v))
	color = list(range(1, K+1))

	q = deque()
	q.append((0, None))

	while q:
		i, color_from = q.popleft()
		tmp = -1
		for node in graph[i]:
			str_ = "{},{}".format(i, node)
			if not edge[str_]:
				use_color = color[tmp]
				if use_color == color_from:
					use_color = color[tmp-1]
					tmp -= 1
				tmp -= 1
				edge[str_] = use_color
				edge["{},{}".format(node, i)] = use_color
				q.append((node, use_color))
	print(K)
	for a, b in ab:
		print(edge["{},{}".format(a-1, b-1)])


if __name__ == "__main__":
	main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

N = INT()
ab = [LIST() for _ in range(N-1)]

graph = defaultdict(list)

edge = [[0]*N for _ in range(N)]
for a, b in ab:
	graph[a-1].append(b-1)
	graph[b-1].append(a-1)

K = 0
for i in graph:
	K = max(K, len(graph[i]))

q = deque()
q.append((0, None))

while q:
	i, color_from = q.popleft()
	can_use_color = list(range(1, K+1))
	if color_from:
		can_use_color.remove(color_from)
	for node in graph[i]:
		if not edge[i][node]:
			use_color = can_use_color.pop()
			edge[i][node] = use_color
			edge[node][i] = use_color
			q.append((node, use_color))

print(K)
for a, b in ab:
	print(edge[a-1][b-1])


Fixed submission:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

def main():
	N = INT()
	ab = [LIST() for _ in range(N-1)]

	graph = defaultdict(list)

	# edge = [[0]*N for _ in range(N)]
	edge = defaultdict(int)
	for a, b in ab:
		graph[a-1].append(b-1)
		graph[b-1].append(a-1)

	K = 0
	for v in graph.values():
		K = max(K, len(v))
	color = list(range(1, K+1))

	q = deque()
	q.append((0, None))

	while q:
		i, color_from = q.popleft()
		tmp = -1
		for node in graph[i]:
			str_ = "{},{}".format(i, node)
			if not edge[str_]:
				use_color = color[tmp]
				if use_color == color_from:
					use_color = color[tmp-1]
					tmp -= 1
				tmp -= 1
				edge[str_] = use_color
				edge["{},{}".format(node, i)] = use_color
				q.append((node, use_color))
	print(K)
	for a, b in ab:
		print(edge["{},{}".format(a-1, b-1)])


if __name__ == "__main__":
	main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

N = INT()
ab = [LIST() for _ in range(N-1)]

graph = defaultdict(list)

edge = [[0]*N for _ in range(N)]
for a, b in ab:
	graph[a-1].append(b-1)
	graph[b-1].append(a-1)

K = 0
for i in graph:
	K = max(K, len(graph[i]))

def DFS(i, color_from):  # color_fromからきた色を使わない
	can_use_color = list(range(1, K+1))
	if color_from:
		can_use_color.remove(color_from)
	for node in graph[i]:
		if not edge[i][node]:
			use_color = can_use_color.pop()
			edge[i][node] = use_color
			edge[node][i] = use_color
			DFS(node, use_color)

DFS(0, None)

print(K)
for a, b in ab:
	print(edge[a-1][b-1])


Fixed submission:
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, atan, degrees
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

def main():
	N = INT()
	ab = [LIST() for _ in range(N-1)]

	graph = defaultdict(list)

	# edge = [[0]*N for _ in range(N)]
	edge = defaultdict(int)
	for a, b in ab:
		graph[a-1].append(b-1)
		graph[b-1].append(a-1)

	K = 0
	for v in graph.values():
		K = max(K, len(v))
	color = list(range(1, K+1))

	q = deque()
	q.append((0, None))

	while q:
		i, color_from = q.popleft()
		tmp = -1
		for node in graph[i]:
			str_ = "{},{}".format(i, node)
			if not edge[str_]:
				use_color = color[tmp]
				if use_color == color_from:
					use_color = color[tmp-1]
					tmp -= 1
				tmp -= 1
				edge[str_] = use_color
				edge["{},{}".format(node, i)] = use_color
				q.append((node, use_color))
	print(K)
	for a, b in ab:
		print(edge["{},{}".format(a-1, b-1)])


if __name__ == "__main__":
	main()