POJ 1258 Agri-Net

很普通的一道关于最小生成树的题，回顾了下kruskal算法的写法。

 

/*Accepted 332K 16MS C++ 987B 2012-07-23 23:03:38 */
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
using namespace std;
const int MAXN = 105;
int p[MAXN], r[MAXN * MAXN], u[MAXN * MAXN], v[MAXN * MAXN], w[MAXN * MAXN];
int n, m;

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

void init()
{
    m = 0;
    int c, i, j;
    for( i = 1; i <= n; i ++)
        for( j = 1; j <= n; j ++)
        {
            scanf( "%d", &c);
            if( i == j) continue;
            u[m] = i, v[m] = j; w[m ++] = c;
        }
}

int cmp( const int i, const int j)
{
    return w[i] < w[j];
}

int kruskal()
{
    int i, j, e, ans = 0;
    int nx, ny;
    for( i = 1; i <= n; i ++)
        p[i] = i;
    for( i = 0; i < m; i ++)
        r[i] = i;
    sort( r, r + m, cmp);
    for( i = 0; i < m; i ++)
    {
        e = r[i];
        nx = find(u[e]), ny = find(v[e]);
        if( nx != ny) {
            p[nx] = ny;
            ans += w[e];
        }
    }
    return ans;
}

int main()
{
    while( scanf( "%d", &n) == 1)
    {
        init();
        printf( "%d\n", kruskal());
    }
    return 0;
}