bzoj1854: [Scoi2010]游戏

可以跑二分图

到第一个不能匹配的点就退出

嗯 还有并查集判环的做法？

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<string>

using namespace std;

void setIO(const string& a) {
    freopen((a+".in").c_str(), "r", stdin);
    freopen((a+".out").c_str(), "w", stdout);
}

const int N = 1000000 + 10, M = 10000 + 10;

#include<vector>
vector<int> G[M];
int mat[M];

void AddEdge(int u, int v) {
    G[u].push_back(v);
}

int vis[N], clk;

bool find(int u) {
    for(unsigned i = 0; i < G[u].size(); i++) {
        int v = G[u][i];
        if(vis[v] != clk) {
            vis[v] = clk;
            if(mat[v] == 0 || find(mat[v])) {
                mat[v] = u;
                return 1;
            }
        }
    }
    return 0;
}

int work(int n) {
    for(int i = 1; i <= n; i++) {
        ++clk;
        if(!find(i)) return i - 1;
    }
    return n;
}

int main() {
    int x, y, n;
    scanf("%d", &n);
    for(int i = 1; i <= n; i++) {
        scanf("%d%d", &x, &y);
        AddEdge(x, i);
        AddEdge(y, i);
    }
    printf("%d
", work(n));
        
    return 0;
}