并查集代码总结

核心代码：

int find(int x){    while(x != root[x])/*循环寻找x对应根的值*/    {        x = root[x];    }    return x;}void unio(int a, int b)/*合并a所在的树的根，和b所在的树的根*/{    int x, y;    x = find(a);/*求a的根*/    y = find(b);/*求b的根*/    if(x != y)    {        root[y] = x;/*让y的根等于x*/    }}

题目：小鑫的城堡http://acm.sdut.edu.cn/onlinejudge2/index.php/Home/Contest/contestproblem/cid/2014/pid/2798.html

#include<stdio.h>#include<stdlib.h>#include<string.h>int root[100555], flag;int house[100555];int find(int x){    while(x != root[x])    {        x = root[x];    }    return x;}void unio(int a, int b){    int x, y;    x = find(a);    y = find(b);    if(x != y)    {        root[y] = x;    }    else flag = 0;//判断是否回路}int max1(int a, int b){    if(a < b) return b;    else return a;}int main(){    int m, a, b, i, max, num;    while(~scanf("%d", &m))    {        max = 0;        num = 0;        memset(house, 0, sizeof(house));        flag = 1;        for(i = 1; i <= 100005; i++)//初始化根        root[i] = i;        for(i = 0; i < m; i++)        {            scanf("%d %d", &a, &b);            if(max < max1(a, b))//找出最大房间号            max = max1(a, b);            house[a]++; house[b]++;            unio(a, b);//合并        }        for(i = 1; i <= max; i++)        {            if(house[i]) num++;//统计房间数        }        if(flag && num == m + 1) printf("Yes\n");//图满足房间数等于路径数加一 && 不允许有回路        else printf("No\n");    }    return 0;}