poj 1088 滑雪 dp

dp[i][j]表示从i,j开始的最长路径，记忆化搜索一下。

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define maxn 120
int dp[maxn][maxn],map[maxn][maxn];
int r,c;
int dfs(int i,int j)
{
    if(dp[i][j]!=-1) return dp[i][j];
    else
    {
        int ans=1;
        if(j+1<=c&&map[i][j]>map[i][j+1]) ans=max(ans,dfs(i,j+1)+1);
        if(j-1>=1&&map[i][j]>map[i][j-1]) ans=max(ans,dfs(i,j-1)+1);
        if(i+1<=r&&map[i][j]>map[i+1][j]) ans=max(ans,dfs(i+1,j)+1);
        if(i-1>=1&&map[i][j]>map[i-1][j]) ans=max(ans,dfs(i-1,j)+1);
        dp[i][j]=ans;
        return ans;
    }
}
int main()
{
    int i,j;
    while(scanf("%d%d",&r,&c)!=EOF)
    {
        for(i=1;i<=r;i++)
            for(j=1;j<=c;j++)
                scanf("%d",&map[i][j]);
        memset(dp,-1,sizeof(dp));
        int Max=-1;
        for(i=1;i<=r;i++)
            for(j=1;j<=c;j++)
            {
                if(dp[i][j]==-1)
                    dp[i][j]=dfs(i,j);
                Max=max(dp[i][j],Max);
            }
        printf("%d
",Max);
    }
    return 0;
}