hdu1142 A Walk Through the Forest —— dijkstra + 记忆化搜索

来源：互联网发布：学法语的软件编辑：程序博客网时间：2024/05/16 06:57

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1142

代码如下：

#include <iostream>#include <cstdio>#include <cstring>#include <cstdlib>#include <string>#include <vector>#include <map>#include <set>#include <queue>#include <sstream>#include <algorithm>using namespace std;#define pb push_back#define mp make_pair#define ms(a, b)  memset((a), (b), sizeof(a))#define eps 0.0000001typedef long long LL;const int INF = 2e9;const LL LNF = 9e18;const int maxn = 2000000+10;const int mod = 1e9+7;int n,m,cost[1005][1005],dis[1005],vis[1005],dp[1005];void dijkstra(int st){    int i,j,k;    memset(vis,0,sizeof(vis));    for(i = 1; i<=n; i++)    {        dis[i] = cost[st][i];    }    dis[st] = 0;    vis[st] = 1;    for(i = 2; i<=n; i++)    {        int minn = INF;        for(j = 1; j<=n; j++)        {            if(!vis[j]&&dis[j]<minn)            {                minn = dis[j];                k = j;            }        }        vis[k] = 1;        for(j = 1; j<=n; j++)        {            if(!vis[j])            dis[j] = min(dis[j], dis[k] + cost[k][j]);        }    }}int DFS(int st){    int sum = 0;    if(dp[st]) return dp[st];    if(st==2) return 1;    for(int i = 1; i<=n; i++)    {        if(cost[st][i]!=INF && dis[st]>dis[i])            sum += DFS(i);    }    dp[st] = sum;    return dp[st];}int main(){    int i,j,u,v,w;    while(scanf("%d",&n) && n)    {        for(i = 1; i<=n; i++)        {            for(j = 1; j<=n; j++)            {                cost[i][j] = (i==j?0:INF);            }        }        scanf("%d",&m);        for(i = 1; i<=m; i++)        {            scanf("%d%d%d",&u,&v,&w);            cost[u][v]=cost[v][u] = w;        }        dijkstra(2);        memset(dp,0,sizeof(dp));        printf("%d\n",DFS(1));    }    return 0;}

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