hdu 5876 Sparse Graph（BFS+并查集）

题目链接：hdu 5876 Sparse Graph

/******************
* Author: Jerakrs
* Time: 2016.10.01
* Problem: 给定一张图不存在边，求从起点S到各个点的距离
* Solve: BFS，遍历点时可以用并查集做路劲压缩，经过的点不需要重复检查
* Complexity: o( n ) 并查集压缩路径复杂度为常数
******************/

#include <cstdio>
#include <cstring>
#include <set>
#include <queue>
#include <algorithm>

using namespace std;
const int maxn = 200005;

int N, M, S, F[maxn], A[maxn];
set<int> G[maxn];

int get(int x) {
return x == F[x] ? x : F[x] = get(F[x]);
}

void init () {
scanf("%d%d", &N, &M);
memset(A, -1, sizeof(A));
for (int i = 1; i <= N + 1; i++) {
F[i] = i;
G[i].clear();
}

int u, v;
for (int i = 0; i < M; i++) {
scanf("%d%d", &u, &v);
G[u].insert(v);
G[v].insert(u);
}
scanf("%d", &S);
}

void solve() {
queue<int> que;
que.push(S);
A[S] = 0;
F[S] = S + 1;

while (!que.empty()) {
int u = que.front();
que.pop();

for (int i = get(1); i <= N; i = get(i+1)) {

if (G[u].find(i) != G[u].end() || i == u)
continue;

A[i] = A[u] + 1;
F[i] = i + 1;
que.push(i);
}
}

int end = (S == N ? N - 1 : N);

for (int i = 1; i <= N; i++) {
if (i == S)
continue;
printf("%d%c", A[i], i == end ? '\n' : ' ');
}

}

int main () {
int cas;
scanf("%d", &cas);
while (cas--) {
init();
solve();
}
return 0;
}