uva 1396 Slim Span

Kruskal 算法

注意数组不要越界，尽量开大点，其他没什么注意，这种算法的水题

#include <cstdio>
#include <cmath>
#include <algorithm>
#include <iostream>
//#define T
///////////////
using namespace std;
const int M = 220;
int f[M];
struct edge
{
    int x;
    int y;
    int u;
};
edge e[10000];
void s_union(int a, int b);
bool cmp(edge a,edge b);
int f_find(int a);
int counter;
int ans;
int n,m;
void inital()
{
    for(int i = 0; i <= 200; i ++)
        f[i] = i;
    counter = 1;
}
bool cmp(edge a,edge b)
{
    return a.u < b.u;
}
int f_find(int a)
{
    if(a != f[a])
        f[a] = f_find(f[a]);
    return f[a];
}
void s_union(int a, int b)
{
    if(a > b)
        f[b] = a;
    else
        f[a] = b;
}
int main()
{
int l,i,j,r;
    while(~scanf("%d %d",&n,&m) && (n||m))
    {
        ans = 0x3f3f3f3f;
        for( i = 0; i < m; i ++)
            scanf("%d %d %d",&e[i].x,&e[i].y,&e[i].u);

            sort(e,e+m,cmp);
            for(j = 0; j < m; j++)
            {
                inital();
                for( i = j; i < m; i++)
                {
                    l = f_find(e[i].x);
                    r = f_find(e[i].y);
                    if(l != r)
                    {
                        s_union(l,r);
                        counter++;
                       // printf("counter ----- %d\n",counter);
                    }
                    if(counter == n)
                    {
                        ans = min(ans,e[i].u - e[j].u);
                        break;
                    }
                }
             }
             if(ans == 0x3f3f3f3f)
                printf("%d\n",-1);
             else
            printf("%d\n",ans);

    }
    return 0;
}