UVA1160 X-Plosives

思路

每个元素设为点，化合物设为边

不能出现k条边k个点的环

直接并查集检查即可

代码

#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
int fa[100100],ans=0,a,b;
void init(void){
    ans=0;
    for(int i=1;i<=100010;i++)
        fa[i]=i;
}
int find(int x){
    return (fa[x]==x)?x:fa[x]=find(fa[x]);
}
void merge(int x,int y){
    if(find(x)==find(y))
        ans++;
    else
        fa[find(x)]=find(y);
}
int main(){
    freopen("test.in","r",stdin);
    freopen("test.out","w",stdout);
    while(scanf("%d",&a)==1){
        init();
        while(a!=-1){
            scanf("%d",&b);
            merge(a,b);
            scanf("%d",&a);
        }
        printf("%d\n",ans);
    }
    return 0;
}