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039.cpp
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40 lines (35 loc) · 746 Bytes
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#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
long long N;
long long A[1 << 18], B[1 << 18];
long long dp[1 << 18];
vector<int> G[1 << 18];
void dfs(int pos, int pre) {
dp[pos] = 1;
for (int i : G[pos]) {
if (i == pre) continue;
dfs(i, pos);
dp[pos] += dp[i];
}
}
int main() {
// Step #1. 入力
cin >> N;
for (int i = 1; i <= N - 1; i++) {
cin >> A[i] >> B[i];
G[A[i]].push_back(B[i]);
G[B[i]].push_back(A[i]);
}
// Step #2. 深さ優先探索（DFS）
dfs(1, -1);
// Step #3. 答えを求める
long long Answer = 0;
for (int i = 1; i <= N - 1; i++) {
long long r = min(dp[A[i]], dp[B[i]]);
Answer += r * (N - r);
}
cout << Answer << endl;
return 0;
}