[luoguP1111] 修复公路（并查集）

传送门

呵呵的最小生成树

——代码

#include <cstdio>
#include <iostream>
#include <algorithm>

#define N 100001

int n, m, sum;
int f[N];

struct node
{
    int x, y, z;
}e[N];

inline int read()
{
    int x = 0, f = 1;
    char ch = getchar();
    for(; !isdigit(ch); ch = getchar()) if(ch == '-') f = -1;
    for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - '0';
    return x * f;
}

inline bool cmp(node x, node y)
{
    return x.z < y.z;
}

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

int main()
{
    int i, j, x, y;
    n = sum = read();
    m = read();
    for(i = 1; i <= n; i++) f[i] = i;
    for(i = 1; i <= m; i++)
    {
        e[i].x = read();
        e[i].y = read();
        e[i].z = read();
    }
    std::sort(e + 1, e + m + 1, cmp);
    for(i = 1; i <= m; i++)
    {
        x = find(e[i].x);
        y = find(e[i].y);
        if(x ^ y)
        {
            f[x] = y;
            sum--;
            if(sum == 1)
            {
                printf("%d
", e[i].z);
                return 0;
            }
        }
    }
    puts("-1");
    return 0;
}