HDU 2120 Ice_cream's world I

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并查集应用之判断环：依次输入每条边，当边的两个点在同一个集合时，环数加一，否则合并。

#include<cstdio>#include<cstring>#include<iostream>#include<iomanip>#include<queue>#include<cmath>#include<stack>#include<map>#include<vector>#include<set>#include<algorithm>using namespace std;typedef long long LL;const int int_max = 0x07777777;const int int_min = 0x80000000;int n, m;int mymap [1100][1100];int root[1100];int find (int x){    while(x!=root[x]){        x = root[x];    }    return x;}void combine (int x, int y){    int xx = find(x);    int yy = find(y);    if(xx!=yy){        root[yy] = xx;    }}int main(int argc, const char * argv[]){    while(scanf("%d %d",&n, &m)!=EOF){        memset(mymap, 0, sizeof(mymap));        for(int i = 0; i < n; i++) root[i] = i;        int result = 0;        for(int i = 0; i < m; i++){            int x,y;            cin >> x >> y;            if(find(x)==find(y)){                result++;            }else{                combine(x, y);            }        }        cout << result << endl;    }}

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