hdu1232 畅通工程

还是并查集，不过我觉得最后判断最少路径自己处理的麻烦了，得去看看大神代码.......

code：

/*ID: yueqiqPROG: numtriLANG: C++*/#include <set>#include <map>#include <ctime>#include <queue>#include <cmath>#include <stack>#include <limits>#include <vector>#include <bitset>#include <string>#include <cstdio>#include <cstring>#include <fstream>#include <string.h>#include <iostream>#include <algorithm>#define Si set<int>#define LL long long#define pb push_back#define PS printf(" ")#define Vi vector<int>#define LN printf("\n")#define lson l,m,rt << 1#define rson m+1,r,rt<<1|1#define SD(a) scanf("%d",&a)#define PD(a) printf("%d",a)#define SET(a,b) memset(a,b,sizeof(a))#define FF(i,a) for(int i(0);i<(a);i++)#define FD(i,a) for(int i(a);i>=(1);i--)#define FOR(i,a,b) for(int i(a);i<=(b);i++)#define FOD(i,a,b) for(int i(a);i>=(b);i--)#define readf freopen("input.txt","r",stdin)#define writef freopen("output.txt","w",stdout)const int maxn = 1001;const int INF = 0x3fffffff;const int dx[]={0,1,0,-1};const int dy[]={1,0,-1,0};const double pi = acos(-1.0);using namespace std;int N,M;bool use[maxn];int num[maxn],pre[maxn];void Make_Set(int k){    num[k]=1;    pre[k]=k;}int Find_Set(int k){    if(k!=pre[k]){        pre[k]=Find_Set(pre[k]);//回溯赋值，压缩路径    }    return pre[k];}//union the set of x,yvoid Union_Set(int x,int y){    x=Find_Set(x);    y=Find_Set(y);    if(x==y) return;    if(num[x]>=num[y]){        pre[y]=x;        num[x]+=num[y];    }else{        pre[x]=y;        num[y]+=num[x];    }}int main(){    while(~scanf("%d",&N)&&N){        SD(M);        SET(use,false);        FOR(i,1,N) Make_Set(i);        int a,b;        FF(i,M){            SD(a);SD(b);            Union_Set(a,b);        }        int k=0;        FOR(i,1,N){            int t=Find_Set(i);            if(!use[t]){                k++;                use[t]=true;            }        }        //puts("------------------------");        PD(k-1);LN;        //puts("------------------------");    }    return 0;}