Constructing Roads (MST)

#include<stdio.h>
#include<algorithm>
using namespace std;
#define S 110
struct edge
{
    int u , v , w ;
}e[S * S];
int n , m ,p[S];//这一这三个变量的位置要小心，不然，嘿嘿

void init ()
{
    for(int i = 1 ; i <= S ; i++)
        p[i] = i ;
}

bool cmp (edge a , edge b)
{
    return a.w < b.w ;
}

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

void kruskal ()
{
    sort (e + 1 , e + m , cmp) ;
    int ans = 0 , x , y ;
    for (int i = 1 ; i < m ; i++) {
        x = find (e[i].u) ;
        y = find (e[i].v) ;
        if (x != y) {
            ans += e[i].w ;
            p[x] = y ;
        }
    }
    printf ("%d\n" , ans) ;
}
int main ()
{
   // freopen ("a.txt" , "r" ,stdin) ;
    int k , built ;
    int x , y ;
    while (~ scanf ("%d" , &n ) ) {
        init () ;
        m = 1 ;
        for (int i = 1 ; i <= n ; i++) {
            for (int j = 1 ; j <= n ; j++) {
                if (j <= i) {
                    scanf ("%d" , &k ) ;
                    continue ;
                }
                scanf ("%d" , &e[m].w) ;
                e[m].u = i ;
                e[m].v = j ;
                m++ ;
            }
        }
        scanf ("%d" , &built );
        for (int i = 0 ; i < built ; i++) {
            scanf ("%d%d" , &x , &y ) ;
            x = find (x) ;
            y = find (y) ;
            p[x] = y ;
        }
        kruskal () ;
    }
    return 0 ;
}