hdu 1688

最短路与次短路条数

#include <stdio.h>
#include <string.h>
#define N 10005
#define INF 0x3f3f3f3f
struct Edge{
    int u,val,next;
}e[2*N];
int p[N],vis[N][2],d[N][2],cnt[N][2];
void add(int n,int m)
{
    int i,x,y,cost,cout = 1;
    for(i = 1 ; i <= n ; i++) p[i] = -1;
    while(m--)
    {
        scanf("%d %d %d",&x,&y,&cost);
        e[cout].u = y;
        e[cout].val = cost;
        e[cout].next = p[x];
        p[x] = cout++;
    }
}
int dijkstra(int s,int t,int n,int m)
{
    int i,x,y,temp,ok;
    for(i = 1 ; i <= n ; i++)
    {
        d[i][0] = INF;
        d[i][1] = INF;
        vis[i][0] = 0;
        vis[i][1] = 0;
    }
    d[s][0] = 0;
    cnt[s][0] = 1;
    for(i = 1 ; i <= 2*n ; i++)
    {
        temp = INF,ok ,x = -1;
        for(y = 1 ; y <= n ;y++)
            if(!vis[y][0]&&temp>d[y][0]) {
                temp = d[y][0];
                ok = 0;
                x = y;
            }
        else if(!vis[y][1]&&temp>d[y][1]) {
            temp = d[y][1];
            ok = 1;
            x = y;
        }
        if(x == -1) break;
        vis[x][ok] = 1;
        for(y = p[x] ; y!=-1; y = e[y].next)
        {
            int newd = d[x][ok]+e[y].val;
            int u = e[y].u;
            if(newd<d[u][0])
            {
                d[u][1] = d[u][0];
                d[u][0] = newd;
                cnt[u][1] = cnt[u][0];
                cnt[u][0] = cnt[x][ok];
            }else if(newd == d[u][0]){
                cnt[u][0] += cnt[x][ok];
            }else if(newd<d[u][1]){
                d[u][1] = newd;
                cnt[u][1] = cnt[x][ok];
            }else if(newd == d[u][1]){
                cnt[u][1]+=cnt[x][ok];
            }
        }
    }
    int num = cnt[t][0];
    if(d[t][0] + 1 == d[t][1]) num+=cnt[t][1];
    return num;
}
int main()
{
    int t,n,m;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d %d",&n,&m);
        add(n,m);
        int s,t;
        scanf("%d %d",&s,&t);
        int ans = dijkstra(s,t,n,m);
        printf("%d
",ans);
    }
    return 0;
}