Largest Rectangular Area Histogram

Algorithms/Largest_Rectangular_Area_Histogram.java

@@ -0,0 +1,62 @@
+//Java program to find maximum rectangular area in linear time 
+
+import java.util.Stack; 
+
+public class RectArea_Histogram 
+{ 
+	static int getMaxArea(int hist[], int n) 
+	{ 
+		// The stack holds indexes of hist[] array 
+		Stack<Integer> s = new Stack<>(); 
+
+		int max_area = 0; // Initialize max area 
+		int top; // To store top of stack 
+		int area_with_top; // To store area with top bar as the smallest bar 
+
+		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.peek()] <= 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 bar. 
+			else
+			{ 
+				top = s.peek();  
+				s.pop(); 
+
+				// Calculate the area with hist[tp] stack as smallest bar 
+				area_with_top = hist[top] * (s.empty() ? i : i - s.peek() - 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) 
+		{ 
+			top = s.peek(); 
+			s.pop(); 
+			area_with_top = hist[top] * (s.empty() ? i : i - s.peek() - 1); 
+
+			if (max_area < area_with_top) 
+				max_area = area_with_top; 
+		} 
+
+		return max_area; 
+
+	} 
+
+
+	public static void main(String[] args) 
+	{ 
+		int hist[] = { 6, 1, 7, 4, 5, 9, 2 }; 
+		System.out.println(getMaxArea(hist, hist.length)); 
+	} 
+} 
+