From 0bf445627b94a5f9ce0fb439fbee44bc50407862 Mon Sep 17 00:00:00 2001
From: Nikhil Jaiswal <nikhiljai111@gmail.com>
Date: Wed, 12 Oct 2022 10:23:43 +0530
Subject: [PATCH] added max_area_histogram.cpp

---
 max_area_histogram.cpp | 73 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 max_area_histogram.cpp

diff --git a/max_area_histogram.cpp b/max_area_histogram.cpp
new file mode 100644
index 0000000..188a3c7
--- /dev/null
+++ b/max_area_histogram.cpp
@@ -0,0 +1,73 @@
+// C++ program to find maximum rectangular area in
+// linear time
+#include <bits/stdc++.h>
+using namespace std;
+
+// The main function to find the maximum rectangular
+// area under given histogram with n bars
+int getMaxArea(int hist[], int n)
+{
+	// Create an empty stack. The stack holds indexes
+	// of hist[] array. The bars stored in stack are
+	// always in increasing order of their heights.
+	stack<int> s;
+
+	int max_area = 0; // Initialize max area
+	int tp; // To store top of stack
+	int area_with_top; // To store area with top bar
+					// as the smallest bar
+
+	// Run through all bars of given histogram
+	int i = 0;
+	while (i < n) {
+		// If this bar is higher than the bar on top
+		// stack, push it to stack
+		if (s.empty() || hist[s.top()] <= hist[i])
+			s.push(i++);
+
+		// If this bar is lower than top of stack,
+		// then calculate area of rectangle with stack
+		// top as the smallest (or minimum height) bar.
+		// 'i' is 'right index' for the top and element
+		// before top in stack is 'left index'
+		else {
+			tp = s.top(); // store the top index
+			s.pop(); // pop the top
+
+			// Calculate the area with hist[tp] stack
+			// as smallest bar
+			area_with_top
+				= hist[tp]
+				* (s.empty() ? i : i - s.top() - 1);
+
+			// update max area, if needed
+			if (max_area < area_with_top)
+				max_area = area_with_top;
+		}
+	}
+
+	// Now pop the remaining bars from stack and calculate
+	// area with every popped bar as the smallest bar
+	while (s.empty() == false) {
+		tp = s.top();
+		s.pop();
+		area_with_top
+			= hist[tp] * (s.empty() ? i : i - s.top() - 1);
+
+		if (max_area < area_with_top)
+			max_area = area_with_top;
+	}
+
+	return max_area;
+}
+
+// Driver code
+int main()
+{
+	int hist[] = { 6, 2, 5, 4, 5, 1, 6 };
+	int n = sizeof(hist) / sizeof(hist[0]);
+
+	// Function call
+	cout << "Maximum area is " << getMaxArea(hist, n);
+	return 0;
+}