TC = O(n) single pass, SC = O(n)

LargestRectangleInHistogram.cpp

@@ -0,0 +1,43 @@
+//TC = O(n) single pass
+//SC = o(n)
+#include <bits/stdc++.h>
+#include <vector>
+#include <string>
+#include <math.h>
+using namespace std;
+#define ll long long
+#define IOS ios_base::sync_with_stdio(false);
+#define print(array)      \
+    for (auto it : array) \
+    cout << it << " "
+#define sortit(array) sort(array.begin(), array.end())
+const int M = 1e9 + 7;
+
+int largestRectangleArea(vector<int> &heights)
+{
+    stack<int> st;
+    int maxarea = 0;
+    int width = 0;
+    int n = heights.size();
+    for (int i = 0; i <= n; i++)
+    {
+        while (!st.empty() && (i == n || heights[st.top()] >= heights[i]))
+        {
+            int height = heights[st.top()];
+            st.pop();
+            if (st.empty())
+                width = i;
+            else
+                width = i - st.top() - 1;
+            maxarea = max(maxarea, width * height);
+        }
+        st.push(i);
+    }
+    return maxarea;
+}
+
+int main()
+{
+    vector<int> heights = {2, 1, 5, 6, 2, 3};
+    cout << largestRectangleArea(heights);
+}