From 52d507339ce64e8d4c9e946643359d0bdbd26287 Mon Sep 17 00:00:00 2001
From: Piyush Gupta <piyush6348@gmail.com>
Date: Wed, 30 Oct 2019 21:56:37 +0530
Subject: [PATCH] largest rectangle in histogram

---
 Arrays/LargestRectangleInHistogram.cpp | 44 ++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 Arrays/LargestRectangleInHistogram.cpp

diff --git a/Arrays/LargestRectangleInHistogram.cpp b/Arrays/LargestRectangleInHistogram.cpp
new file mode 100644
index 0000000..d68d25b
--- /dev/null
+++ b/Arrays/LargestRectangleInHistogram.cpp
@@ -0,0 +1,44 @@
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+int largestRectangleArea(vector<int>& heights)
+{
+    heights.push_back(0);
+    int n = heights.size();
+    stack<int> stk;
+    int ans = 0;
+    for (int i = 0; i < n; i++) {
+        if (stk.empty() || heights[stk.top()] <= heights[i])
+            stk.push(i);
+        else {
+            while (!stk.empty() && heights[stk.top()] > heights[i]) {
+                int barHeight = heights[stk.top()];
+                stk.pop();
+                int area = 0;
+                if (stk.empty())
+                    area = i * barHeight;
+                else
+                    area = (i - 1 - (stk.top() + 1) + 1) * barHeight;
+                ans = max(ans, area);
+            }
+            stk.push(i);
+        }
+    }
+    return ans;
+}
+
+int main() {
+  vector<int> array;
+
+  int number;
+
+  while (cin >> number) {
+    array.push_back(number);
+  }
+
+  cout << largestRectangleArea(array) << endl;
+
+  return 0;
+}