hdoj1232 畅通工程（并查集）

题目链接

http://acm.hdu.edu.cn/showproblem.php?pid=1232

思路

使用并查集求解。

代码

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;

const int N = 1000 + 10;
int p[N];

void make_set(int n)
{
    for (int i = 1; i <= n; i++)
        p[i] = -1;
}

int find_root(int i)
{
    if (p[i] == -1)
        return i;
    else
    {
        int t = find_root(p[i]);    //路径压缩
        p[i] = t;
        return t;
    }
}

void union_set(int a, int b)
{
    int ra = find_root(a);
    int rb = find_root(b);
    if (ra != rb)
        p[ra] = rb;

}

int main()
{
    //freopen("hdoj1232.txt", "r", stdin);
    int n, m;
    while (scanf("%d%d", &n, &m) == 2 && n)
    {
        make_set(n);
        int a, b;
        for (int i = 0; i < m; i++)
        {
            scanf("%d%d", &a, &b);
            union_set(a, b);
        }
        int ans = 0;
        for (int i = 1;i <= n;i++)
            if (p[i] == -1) ans++;
        printf("%d\n", ans - 1);
    }
    return 0;
}