MST pku 1258 AgriNet

# include <cstdio>
# include <algorithm>

using namespace std;

# define N 100 + 5
# define M 5000 + 5

int n, m;
int p[N];
int u[M], v[M], w[M], r[M];

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

int cmp(int x, int y) {return w[x]<w[y];}
int find(int x) {return x==p[x] ? x:(p[x]=find(p[x]));}
int kruskal(int n, int m)
{
    int ret = 0;
    for (int i = 1; i <= n; ++i) p[i] = i;
    for (int i = 1; i <= m; ++i) r[i] = i;
    sort(r+1, r+1+m, cmp);
    for (int i = 1; i <= m; ++i)
    {
        int e = r[i];
        int x = find(u[e]);
        int y = find(v[e]);
        if (x != y)
        {
            ret += w[e];
            p[y] = x;
        }
    }
    return ret;
}

int main()
{    
    while (~scanf("%d", &n))
    {
        read_graph();
        printf("%d\n", kruskal(n, m));
    }
    
    return 0;
}