nyoj--115 城市平乱（最短路径）

题解

#include <iostream>
#include <cstdio>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;

const int maxn = 1005;
const int inf  = 100001;
int   g[maxn][maxn], a[maxn], d[maxn], v[maxn];
int   n, m, p, q, t;

int dijkstra(int s)
{
memset(v, 0, sizeof(v));
fill(d, d + maxn, inf);
d[s] = 0;
for(int i = 1; i <= m; ++i)
{
int x, Max = inf;
for(int y = 1; y <= m; ++y)
if(!v[y] && d[y] <= Max) Max = d[x = y];
v[x] = 1;
for(int y = 1; y <= m; ++y) d[y] = min(d[y], d[x] + g[x][y]);
}
return d[q];
}

int main()
{
//freopen("data.in", "r", stdin);
for(cin >> t; t--; )
{
cin >> n >> m >> p >> q;
for(int i = 0; i <= m; ++i) fill(*(g + i), *(g + i) + maxn, inf);
for(int i = 0; i < n; ++i) cin >> a[i];
int u, v, w;
for(int i = 1; i <= p; ++i){
scanf("%d %d %d", &u, &v, &w);
g[u][v] = g[v][u] = min(g[u][v], w);
}
int ans = inf;
for(int i = 0; i < n; ++i)
{
ans = min(ans, dijkstra(a[i]));
}
cout << ans << endl;
}

return 0;
}