并查集

来源：互联网发布：nginx 域名www跳转编辑：程序博客网时间：2024/06/15 13:00

并查集完成不相交集合的合并与查找工作，时间复杂度为常数。主要进行一下3个操作：

1、合并两个集合；

2、查询一个元素在哪个集合；

3、判断两个元素是否在同一个集合；

查询操作：

int find(int x){        reutrn  x== fa[x] ? x : fa[x] = find(fa[x]);}

合并操作

void merge(int x,int y){   int u = find(x);   int v = find(y);   if (u != v)   fa[u] = v;}

POJ 1703 简单并查集应用：

#include<cstdio>#include<cstring> #include<cmath>#include<cstdlib>#include<climits>#include<cctype>#include<iostream>#include<algorithm>#include<queue>#include<vector>#include<set>#include<stack>#include<string>#include<map>#define ll long long#define INF INT_MAX#define eps 1e-6 #define MAX 100010using namespace std;  int fa[MAX],mark[MAX];            //mark[i] 记录i的敌人； int find(int x){return (x == fa[x]) ? x : fa[x] = find(fa[x]);}         void merge(int x ,int y){int u = find(x);int v = find(y);if (u != v)                     fa[u] = v;}int main(){int T,n,m;scanf("%d",&T);char s[5];while (T--){scanf("%d%d",&n,&m);int u,v; for(int i=1; i<=n; i++) fa[i] = i;memset(mark,0,sizeof(mark));for (int i=1; i<=m; i++){scanf("%s%d%d",s,&u,&v);if (s[0] == 'A'){if (find(u) == find(mark[v])) printf("In different gangs.\n");else if (find(u) == find(v))  printf("In the same gang.\n");else printf("Not sure yet.\n");}else {if (mark[u]) merge(mark[u],v);if (mark[v]) merge(mark[v],u);mark[u] = v;mark[v] = u;}} }return 0;}

0 0