POJ 1703 Find them, Catch them 种类并查集（入门）

/***     种类并查集入门题：*       这题开始做的时候总是MLE 因为在get_together(x, y)之前没有判断find(x) != find(y)*    因为，如果find(x) == find(y) 的时候，x，y在同个集合中，那么在合并的时候，根节点的fa = y；*    而y的fa又等于根节点，就会变成没有根节点。当下次在调用find(y)的时候就会不停的递归，导致MLE.*    还有，就是看discuss上说，如果find()函数是用迭代而非递归写的话会TLE。而用递归则MLE*    总之在合并之前要先判断find(x) != find(y) 才可以继续合并。*/#include <cstdio>#include <cstring>#include <cmath>#include <string>#include <algorithm>#define INF 0x7fffffff#define MAXS 100005#define LL long longusing namespace std;struct Person {    int re, fa;} guys[MAXS];void init(int n) {    for(int i = 1; i <= n; i ++) {        guys[i].fa = i;        guys[i].re = 1;    }}int find(int x) {    int fa = guys[x].fa;    if(fa == x) return fa;    else {        guys[x].fa = find(fa);        guys[fa].re == guys[x].re ? guys[x].re = 1 : guys[x].re = 0;        return guys[x].fa;    }}bool judge(int x, int y) {    if(guys[x].re == guys[y].re) return true;    else return false;}void get_together(int x, int y) {    int xfa = find(x);    guys[xfa].fa = y;    if(guys[x].re == 1) guys[xfa].re = 0;    else                guys[xfa].re = 1;}int main(){    int t, N, M, a, b;    char cmd;    scanf("%d", &t);    while(t --) {        scanf("%d%d", &N, &M);        init(N);        for(int i = 1; i <= M; i ++) {            scanf("\n%c", &cmd);            scanf("%d%d", &a, &b);            if(cmd == 'A') {                if(find(a) != find(b)) {                    printf("Not sure yet.\n");                } else {                    if(judge(a, b)) printf("In the same gang.\n");                    else        printf("In different gangs.\n");                }            }            else if(cmd == 'D') {                if(find(a) != find(b))                    get_together(a, b);            }        }    }    return 0;}