hdu 5423 Rikka with Tree（水）

题目链接：hdu 5423 Rikka with Tree

#include <cstdio>#include <cstring>#include <vector>#include <algorithm>using namespace std;const int maxn = 1005;int N, D[maxn], V[maxn];vector<int> G[maxn];void dfs (int u, int d) {D[d]++;V[u] = 1;for (int i = 0; i < G[u].size(); i++) {int v = G[u][i];if (V[v]) continue;dfs(v, d + 1);}}void init () {memset(D, 0, sizeof(D));memset(V, 0, sizeof(V));for (int i = 0; i <= N; i++) G[i].clear();int u, v;for (int i = 1; i < N; i++) {scanf("%d%d", &u, &v);G[u].push_back(v);G[v].push_back(u);}dfs(1, 0);}bool judge () {for (int i = 0; i < N-1 && D[i]; i++) {if (D[i] > 1 && D[i+1]) return false;}return true;;}int main () {while (scanf("%d", &N) == 1) {init();printf("%s\n", judge() ? "YES" : "NO");}return 0;}