CODEFORCE 120F

cf120f.md

cpp 版显示 wrong answer，没有输出, python 版显示 runtime error，没有提示，但是本地测试过测试用例都没有问题，算法应该是正确的。

cf120f.py

cases = int(raw_input())
sumLength = 0

def maxHeight(edgeDict, root, visited=set([])):
    visited.add(root);
    return max([maxHeight(edgeDict, child, visited) if child not in visited else -1 for child in edgeDict[root]]) + 1

for case in range(cases):
    edgeDict = {}
    line = [int(i) for i in raw_input().split(' ')]
    ni = line[0];
    for i in range(ni - 1):
        u = line[i * 2 + 1]
        v = line[i * 2 + 2]

        if u in edgeDict:
            edgeDict[u].append(v)
        else:
            edgeDict[u] = [v]

        if v in edgeDict:
            edgeDict[v].append(u)
        else:
            edgeDict[v] = [u]

    sumLength += max([maxHeight(edgeDict, i, set([])) for i in range(1, ni + 1)])

print sumLength