<p>Given a <code>rows x cols</code>&nbsp;binary <code>matrix</code> filled with <code>0</code>&#39;s and <code>1</code>&#39;s, find the largest rectangle containing only <code>1</code>&#39;s and return <em>its area</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/09/14/maximal.jpg" style="width: 402px; height: 322px;" />
<pre>
<strong>Input:</strong> matrix = [[&quot;1&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;],[&quot;1&quot;,&quot;0&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;],[&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;],[&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;]]
<strong>Output:</strong> 6
<strong>Explanation:</strong> The maximal rectangle is shown in the above picture.
</pre>

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

<pre>
<strong>Input:</strong> matrix = [[&quot;0&quot;]]
<strong>Output:</strong> 0
</pre>

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

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

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

<ul>
	<li><code>rows == matrix.length</code></li>
	<li><code>cols == matrix[i].length</code></li>
	<li><code>1 &lt;= row, cols &lt;= 200</code></li>
	<li><code>matrix[i][j]</code> is <code>&#39;0&#39;</code> or <code>&#39;1&#39;</code>.</li>
</ul>

class Solution {
public:
    int solve(vector<int> &hist) {
        stack<int> st;
        int i =0;
        int ans = 0;
        while (i<hist.size() ) {
            if (st.empty()|| hist[st.top()] <= hist[i]) {
                // if (st.empty()) {
                //     ans = max(ans, hist[i] * (i+1));
                // }
                // else {
                //     ans = max(ans, hist[i] * (i-st.top()));
                // }
                st.push(i);
                i++;
                continue;
            }
            int prev = st.top(); st.pop();
            ans = max(ans, (i-(st.empty()? 0: st.top()+1))*hist[prev]);
        }
        while(!st.empty()) {
            int top = st.top(); st.pop();
            ans = max(ans, ((int)hist.size() - ((st.empty()? 0: st.top()+1)))* hist[top]);
        }
        return ans;
    }
    int maximalRectangle(vector<vector<char>>& matrix) {
        int n = matrix.size();
        int m = matrix[0].size();
        vector<int> hist(m);
        int ans = 0;
        for (int i=0;i<n;i++) {
            for (int j=0;j<m;j++) {
                if (matrix[i][j] == '0') hist[j] = 0;
                else hist[j]++;
                cout<<hist[j]<<" ";
            }
            cout<<endl;
            ans = max(ans, solve(hist));
            cout<<solve(hist)<<endl;
        }
        return ans;
    }
};
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