标签：hdu   记忆化搜索   最短路   

A Walk Through the Forest

5 6
1 3 2
1 4 2
3 4 3
1 5 12
4 2 34
5 2 24
7 8
1 3 1
1 4 1
3 7 1
7 4 1
7 5 1
6 7 1
5 2 1
6 2 1
0

2
4

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int const INF = 0x3fffffff;
int const MAX = 1005;
int dis[MAX], dp[MAX];
int map[MAX][MAX];
bool vis[MAX];
int n, m;

void Dijkstra(int v0)
{
    memset(vis, false, sizeof(vis));
    for(int i = 1; i <= n; i++)
        dis[i] = INF;
    for(int i = 1; i <= n; i++)
        dis[i] = map[v0][i];
    vis[v0] = true;
    dis[v0] = 0;
    for(int i = 1; i < n; i++)
    {
        int u = 0, mi = INF;
        for(int j = 1; j <= n; j++)
        {
            if(!vis[j] && dis[j] < mi)
            {
                mi = dis[j];
                u = j;
            }
        }
        vis[u] = true;
        for(int k = 1; k <= n; k++)
            if(!vis[k])
                dis[k] = min(dis[k], dis[u] + map[u][k]);
    }
}

int DFS(int x)
{
    if(dp[x])
        return dp[x];
    if(x == 2)
        return 1;
    int tmp = 0;
    for(int i = 1; i <= n; i++)
        if(dis[x] > dis[i] && map[x][i] != INF)
            tmp += DFS(i);
    return dp[x] = tmp;
}

int main()
{
    while(scanf("%d", &n) != EOF && n)
    {
        scanf("%d", &m);
        for(int i = 1; i <= n; i++)
            for(int j = 1; j <= n; j++)
                map[i][j] = INF;
        for(int i = 0; i < m; i++)
        {
            int u, v, w;
            scanf("%d %d %d", &u, &v, &w);
            map[u][v] = map[v][u] = w;
        }
        Dijkstra(2);
        memset(dp, 0, sizeof(dp));
        printf("%d\n", DFS(1));
    }
}

HDU 1142 A Walk Through the Forest (Dijkstra + 记忆化搜索 好题)

标签：hdu   记忆化搜索   最短路   

原文地址：http://blog.csdn.net/tc_to_top/article/details/45276461