<p>Given a <code>matrix</code>&nbsp;and a <code>target</code>, return the number of non-empty submatrices that sum to <font face="monospace">target</font>.</p>

<p>A submatrix <code>x1, y1, x2, y2</code> is the set of all cells <code>matrix[x][y]</code> with <code>x1 &lt;= x &lt;= x2</code> and <code>y1 &lt;= y &lt;= y2</code>.</p>

<p>Two submatrices <code>(x1, y1, x2, y2)</code> and <code>(x1&#39;, y1&#39;, x2&#39;, y2&#39;)</code> are different if they have some coordinate&nbsp;that is different: for example, if <code>x1 != x1&#39;</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/09/02/mate1.jpg" style="width: 242px; height: 242px;" />
<pre>
<strong>Input:</strong> matrix = [[0,1,0],[1,1,1],[0,1,0]], target = 0
<strong>Output:</strong> 4
<strong>Explanation:</strong> The four 1x1 submatrices that only contain 0.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> matrix = [[1,-1],[-1,1]], target = 0
<strong>Output:</strong> 5
<strong>Explanation:</strong> The two 1x2 submatrices, plus the two 2x1 submatrices, plus the 2x2 submatrix.
</pre>

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

<pre>
<strong>Input:</strong> matrix = [[904]], target = 0
<strong>Output:</strong> 0
</pre>

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

<ul>
	<li><code>1 &lt;= matrix.length &lt;= 100</code></li>
	<li><code>1 &lt;= matrix[0].length &lt;= 100</code></li>
	<li><code>-1000 &lt;= matrix[i][j] &lt;= 1000</code></li>
	<li><code>-10^8 &lt;= target &lt;= 10^8</code></li>
</ul>

class Solution {
public:
    int numSubmatrixSumTarget(vector<vector<int>>& m, int t) {
        vector<vector<int>>v(m.size(),vector<int>(m[0].size(),0));
        for(int i=0;i<m.size();i++){
            for(int j=0;j<m[0].size();j++){
                int sum=m[i][j];
                if(i>0){
                    sum+=v[i-1][j];
                }
                if(j>0){
                    sum+=v[i][j-1];
                }
                if(i>0&&j>0){
                    sum-=v[i-1][j-1];
                }
                v[i][j]=sum;
            }
        }
        for(int i=0;i<m.size();i++){
            for(int j=0;j<m[0].size();j++){
                cout<<v[i][j]<<" ";
            }
            cout<<endl;
        }
        int ans=0;
        for(int r1=0;r1<m.size();r1++){
            for(int r2=r1;r2<m.size();r2++){
                unordered_map<int,int>map;
                for(int j=0;j<m[0].size();j++){
                    int sum=v[r2][j];
                    if(r1>0){
                        sum-=v[r1-1][j];
                    }
                    if(sum==t){
                        ans++;
                    }
                    ans+=map[sum-t];
                    map[sum]++;
                }
            }
        }

        return ans;
    }
};
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