POJ_1088_dfs

http://poj.org/problem?id=1088

dfs过程中，保存经历过的点的最大滑雪距离，依次遍历每一个点的最大距离即可。

#include<iostream>
#include<cstdio>
using namespace std;
int r,c,a[][],maxlen[][] = {};
int dir[][] = {-,,,-,,,,};
int dfs(int x,int y)
{
    int maxx = ,len;
    for(int i = ;i < ;i++)
    {
        int xx = x+dir[i][],yy = y+dir[i][];
        if(xx <  || xx > r || yy <  || yy > c)    continue;
        if(a[x][y] > a[xx][yy])
        {
            if(maxlen[xx][yy])  len = maxlen[xx][yy]+;
            else    len = dfs(xx,yy)+;
            maxx = max(maxx,len);
        }
    }
    maxlen[x][y] = maxx;
    return maxx;
}
int main()
{
    cin >> r >> c;
    for(int i = ;i <= r;i++)
    {
        for(int j = ;j <= c;j++)   cin >> a[i][j];
    }
    int ans = ,len;
    for(int i = ;i <= r;i++)
    {
        for(int j = ;j <= c;j++)
        {
            if(maxlen[i][j] == )
            {
                len = dfs(i,j);
                ans = max(ans,len);
            }
        }
    }
    cout << ans << endl;
    return ;
}