nefu 18 滑雪

http://acm.nefu.edu.cn/JudgeOnline/problemShow.php?problem_id=18

题意： 找一条从高到低的最长的路的长度；

思路：记忆化搜索，但是不知道在那个地方开始或者结束，所以所有的点都走一遍：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<stdlib.h>
#include<algorithm>
using namespace std;
const int maxn = 100 + 10;
int dp[maxn][maxn];
int a[maxn][maxn];
int derict[][2] =
{
-1,0,
1,0,
0,1,
0,-1
};
int n, m;
int dfs(int x, int y)
{
if (dp[x][y] != -1)
return dp[x][y];
int maxs = 0;
for (int i = 0; i < 4; i++)
{
int xx = x + derict[i][0], yy = y + derict[i][1];
if (xx >= 1 && xx <= n && yy >= 1 && yy <= m && a[x][y] > a[xx][yy])
{
maxs = max(maxs, dfs(xx, yy));
}
}
return dp[x][y] = maxs + 1;
}
int main()
{

while (~scanf("%d%d", &n, &m))
{
memset(dp, -1, sizeof(dp));
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= m; j++)
scanf("%d",&a[i][j]);
}
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= m; j++)
dfs(i, j);
}
int ans = 0;
for (int i = 1; i <= n; i++)
{
for (int j = 1; j <= m; j++)
{
ans = max(ans, dp[i][j]);
}
}
cout << ans << endl;
}
return 0;
}