迪杰斯特拉

const int maxn=10000+5;
const int INF=1e9;
int mat[maxn][maxn];
int visit[maxn],dis[maxn];
int n;

int dijkstra(int a,int b)    //a到b的最短路径
{
    memset(visit,0,sizeof(visit));
    for(int i = 1; i <= n; i++)
        dis[i] = mat[a][i];       //最初的源点赋值
    visit[a] =  true;
    for(int i = 1; i <= n; i++)
    {
        int Min = INF;
        int pos;
        for(int j = 1; j <= n; j++) //找的最近的点当中转点
            if(Min > dis[j] && visit[j] == 0)
            {
                Min = dis[j];
                pos = j;
            }
        visit[pos] = true;          //避免重复访问
        for(int j = 1; j <= n; j++)
            if(dis[j] > dis[pos] + mat[pos][j] && visit[j] == 0)  //松弛
                dis[j] = dis[pos] + mat[pos][j];
    }
    return dis[b];
}