HDU 1879 继续畅通工程——最小生成树

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <cmath>

using namespace std;

const int maxn = 110;

int par[maxn], ran[maxn];

void init(int n) {
    for (int i = 0; i <= n; i++) {
        par[i] = i, ran[i] = 0;
    }
}

int seek(int x) {
    if (par[x] == x) return x;
    else return par[x] = seek(par[x]);
}

void unite(int x, int y) {
    x = seek(x), y = seek(y);
    if (x == y) return;
    if (ran[x] == ran[y]) par[x] = y;
    else {
        par[y] = x;
        if (ran[x] == ran[y]) ran[x]++;
    }
}

struct Edge {
    int u, v;
    double cost;
    bool operator < (const Edge &another) const {
        return cost < another.cost;
    }
}edge[maxn*maxn];

int main()
{
    int n, u, v, cost, flag;
    while (scanf("%d", &n) == 1 && n) {
        int len = n * (n - 1) / 2;
        int edge_cnt = 0, cnt = 0;
        init(n);
        for (int i = 1; i <= len; i++) {
            scanf("%d %d %d %d", &u, &v, &cost, &flag);
            if (flag == 1) {
                if (seek(u) != seek(v)) {
                    cnt++;
                    unite(u, v);
                }
            }
            else if (flag == 0) {
                edge_cnt++;
                edge[edge_cnt].u = u, edge[edge_cnt].v = v, edge[edge_cnt].cost = cost;
            }
        }
        sort(edge + 1, edge + 1 + edge_cnt);
        int ans = 0;
        for (int i = 1; i <= edge_cnt; i++) {
            if (cnt == n - 1) break;
            if (seek(edge[i].u) != seek(edge[i].v)) {
                cnt++;
                ans += edge[i].cost;
                unite(edge[i].u, edge[i].v);
            }
        }
        printf("%d\n", ans);
    }
    return 0;
}