<p>Given an <code>m x n</code> integers <code>matrix</code>, return <em>the length of the longest increasing path in </em><code>matrix</code>.</p>

<p>From each cell, you can either move in four directions: left, right, up, or down. You <strong>may not</strong> move <strong>diagonally</strong> or move <strong>outside the boundary</strong> (i.e., wrap-around is not allowed).</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/05/grid1.jpg" style="width: 242px; height: 242px;" />
<pre>
<strong>Input:</strong> matrix = [[9,9,4],[6,6,8],[2,1,1]]
<strong>Output:</strong> 4
<strong>Explanation:</strong> The longest increasing path is <code>[1, 2, 6, 9]</code>.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/27/tmp-grid.jpg" style="width: 253px; height: 253px;" />
<pre>
<strong>Input:</strong> matrix = [[3,4,5],[3,2,6],[2,2,1]]
<strong>Output:</strong> 4
<strong>Explanation: </strong>The longest increasing path is <code>[3, 4, 5, 6]</code>. Moving diagonally is not allowed.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> matrix = [[1]]
<strong>Output:</strong> 1
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == matrix.length</code></li>
	<li><code>n == matrix[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 200</code></li>
	<li><code>0 &lt;= matrix[i][j] &lt;= 2<sup>31</sup> - 1</code></li>
</ul>

class Solution {
public:
    bool isValid(int i, int j, vector<vector<int>>& matrix, int px, int py){
        if(i<0 || j<0 || i>=matrix.size() || j>=matrix[0].size() || matrix[i][j]<=matrix[px][py])
            return false;
        return true;
    }
    int memo[202][202];
    int dping(int i, int j, vector<vector<int>>& matrix){
        long res=1;

        if(memo[i][j]!=-1)
            return memo[i][j];

        for(int x=-1;x<2;x++){
            for(int y=-1;y<2;y++){
                if((!x&&y) || (!y&&x)){
                    int dx=x+i;
                    int dy=y+j;
                    if(isValid(dx, dy, matrix, i, j)){
                        // cout<<dx<<" "<<dy<<endl;
                        long len=dping(dx,dy,matrix)+1;
                        res=max(res,len);
                    }
                }
            }
        }
        return memo[i][j]=res;
    }

    int longestIncreasingPath(vector<vector<int>>& matrix) {
        int n=matrix.size(), m=matrix[0].size();
        int ans=0;
        memset(memo,-1,sizeof(memo));
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                // cout<<"i-"<<i<<"  j-"<<j<<endl;
                ans=max(ans,dping(i,j,matrix));
            }
        }
        return ans;
    }
};
18859