POJ - 2236 并查集

               思路：当一个点被修复时，将它标记为1，并把它所有能到达的点合并即可。

AC代码

#include <cstdio>
#include <cmath>
#include <cctype>
#include <algorithm>
#include <cstring>
#include <utility>
#include <string>
#include <iostream>
#include <map>
#include <set>
#include <vector>
#include <queue>
#include <stack>
using namespace std;
#pragma comment(linker, "/STACK:1024000000,1024000000")
#define eps 1e-10
#define inf 0x3f3f3f3f
#define PI pair<int, int>
typedef long long LL;
const int maxn = 1000 + 5;
struct node{
int x, y;
}pos[maxn];
int p[maxn], vis[maxn];

int find(int x) {
return p[x] == x ? x : p[x] = find(p[x]);
}

void unionset(int x, int y) {
int px = find(x), py = find(y);
if(px != py) p[px] = py;
}

int main() {
int n, d;
scanf("%d%d", &n, &d);
memset(vis, 0, sizeof(vis));
for(int i = 1; i <= n; ++i) p[i] = i;
for(int i = 1; i <= n; ++i) scanf("%d%d", &pos[i].x, &pos[i].y);
getchar();
char s[20];
while(fgets(s, sizeof(s), stdin) != NULL) {
char op;
int a, b;
if(s[0] == 'S') {
sscanf(s, "%c %d %d", &op, &a, &b);
int rx = find(a), ry = find(b);
if(rx == ry) printf("SUCCESS\n");
else printf("FAIL\n");
}
else {
sscanf(s, "%c %d", &op, &a);
vis[a] = 1;
int x = pos[a].x, y = pos[a].y;
for(int i = 1; i <= n; ++i) {
if(a == i || !vis[i]) continue;
int x1 = pos[i].x, y1 = pos[i].y;
if((x-x1)*(x-x1) + (y-y1)*(y-y1) <= d*d) {
unionset(a, i);
}
}
}
}
return 0;
}

如有不当之处欢迎指出！