poj2387 Til the Cows Come Home

解题思路：最短路的模板题,注意一个细节处理即可。

见代码：

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define inf 0x3f3f3f3f
const int maxn = 1005;
int vis[maxn], w[maxn][maxn], d[maxn], t, n;

void Dijkstra()
{
    for(int i = 1; i <= n; i++) d[i] = w[i][n];
    for(int i = 1; i <= n; i++)
    {
        int k = -1;
        int min1 = inf;
        for(int j = 1; j <= n; j++)
        {
            if(vis[j]) continue;
            if(d[j] < min1)
            {
                min1 = d[j];
                k = j;
            }
        }
        if(k == -1) break;
        vis[k] = 1;
        for(int j = 1; j <= n; j++)
        {

            if(vis[j]) continue;
            if(d[j] > d[k] + w[k][j] && w[k][j] < inf)
            {
                   d[j] = d[k] + w[k][j];
            }
        }
    }
    return ;
}

int main()
{
    int x, y, len;
    while(~scanf("%d %d", &t, &n))
    {
        for(int i = 1; i <= n; i++)
        for(int j = 1; j <= n; j++)
        {
            if(i == j) w[i][j] = 0;
            else w[i][j] = w[j][i] = inf;
        }
        memset(vis, 0, sizeof(vis));
        //for(int i = 1; i <= n; i++) d[i] = inf;
        //d[n] = 0;
        while(t-- )
        {
            scanf("%d %d %d", &x, &y, &len);
            //w[x][y] = w[y][x] = len; 刚开始没有进行if判断
            if(w[x][y] > len) w[y][x] = w[x][y] = len;
        }
        Dijkstra();
        printf("%d\n", d[1]);
    }
    return 0;
}