题目链接：点击链接
题意:求生成树，使得最大边与最小边差最小，输出最小值；
枚举边更新答案。
#include <stdio.h>
#include <iostream>
#include <string.h>
#include <algorithm>
#include <math.h>
#include <stack>
#include <queue>
using namespace std;
const int MAXN = 110;//点
const int MAXM = 510;//边
int f[MAXM];//并查集使用
struct Edge
{
int u, v, w;
}edge[MAXM];
int tol;//边数 初始化 0
void addedge(int u, int v, int w)
{
edge[tol].u = u;
edge[tol].v = v;
edge[tol++].w = w;
}
bool cmp(Edge a, Edge b)
{
return a.w < b.w;
}
int find(int x)
{
if (f[x] == -1)
return x;
else
return f[x] = find(f[x]);
}
int kruskal(int n)
{
sort(edge, edge + tol, cmp);
int cnt ;
int ans = 1e9, ok = 0;
int MAX;
for (int j = 0; j < tol; j++)
{
MAX = -1;
memset(f, -1, sizeof(f));
cnt = 0;
for (int i = j; i < tol; i++)
{
int u = edge[i].u;
int v = edge[i].v;
int w = edge[i].w;
MAX = max(MAX, w);
int t1 = find(u);
int t2 = find(v);
if (t1 != t2)
{
f[t1] = t2;
cnt++;
}
if (cnt == n - 1)
break;
}
if (cnt == n - 1)
{
ok = 1;
ans = min(ans, MAX - edge[j].w);
}
}
if (ok)
return ans;
else
return -1;
}
int n, m;
int u, v, w;
int main()
{
while (scanf("%d%d", &n, &m) != EOF)
{
if (n == 0 && m == 0)
break;
tol = 0;
for (int i = 0; i < m; i++)
{
scanf("%d%d%d", &u, &v, &w);
addedge(u, v, w);
}
int ans = kruskal(n);
printf("%d\n", ans);
}
return 0;
}
