POJ 1287 Networking - (MST - Kruskal+并查集)

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题目链接：http://poj.org/problem?id=1287

#include <stdio.h>  
#include <vector>   
#include <algorithm>
#include <cmath>
#include <queue>
using namespace std;

//POJ 2560 Freckles

typedef struct Edge_info
{
    int length;
    int in, out;
    Edge_info() {}
    Edge_info(int i, int o, int l)
        : in(i), out(o), length(l) {}
};

typedef struct
{
    bool operator()(const Edge_info& lhs, const Edge_info& rhs)
    {
        return lhs.length > rhs.length;
    }
}Comp;

inline int getFather(int *p, int x)
{
    if (p[x] == x)return x;
    p[x] = getFather(p, p[x]);
    return p[x];
}

inline void un(int *p, int x, int y)
{
    int fx = getFather(p, x);
    int fy = getFather(p, y);
    p[fx] = fy;
}

inline bool judge(int *p, int x, int y)
{
    return getFather(p, x) == getFather(p, y);
}

int main()
{
    int P, R;
    while (~scanf("%d%d", &P, &R))
    {
        if (P == 0)break;
        if (P == 1)
        {
            printf("0\n");
            getchar();
            continue;
        }
        vector<Edge_info> edge(R);
        int edge_count = 0;
        int A, B, C;
        for (int i = 0; i < R; ++i)
        {
            scanf("%d%d%d", &A, &B, &C);
            A--; B--;
            edge[i] = Edge_info(A, B, C);
        }
        priority_queue<Edge_info, vector<Edge_info>, Comp> pq(Comp(), edge);//maximum heap
        //Kruskal
        int *p = new int[P];
        for (int i = 0; i < P; ++i)
            p[i] = i;
        int total_length = 0;
        for (int i = 0; i < P - 1; ++i)
        {
            bool isValid = false;
            while (!isValid)
            {
                Edge_info e = pq.top(); pq.pop();
                if (judge(p, e.in, e.out))continue;
                isValid = true;
                un(p, e.in, e.out);
                total_length += e.length;
            }
        }
        printf("%d\n", total_length);
        delete[] p;
        getchar();
    }
    system("pause");
    return 0;
}