Largest Rectangle in Histogram

Largest Rectangle in Histogram

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Given n non-negative integers representing the histogram's bar height where the width of each bar is 1, find the area of largest rectangle in the histogram.

Above is a histogram where width of each bar is 1, given height = [2,1,5,6,2,3].

The largest rectangle is shown in the shaded area, which has area = 10 unit.

For example,
Given height = [2,1,5,6,2,3],
return 10.

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public class Solution {         public int largestRectangleArea(int[] height) {        int [] leftSmall = new int[height.length];        int [] rightSmall = new int[height.length];        Stack<PositionNode> smallStack = new Stack<PositionNode>();        for (int i = 0; i < height.length; i++) {            while (!smallStack.isEmpty() && smallStack.peek().height >= height[i]){                smallStack.pop();            }            if (!smallStack.isEmpty())             {                leftSmall[i] = smallStack.peek().pos;             }  else {                leftSmall[i] = -1;             }            smallStack.push(new PositionNode(i,height[i]));        }            smallStack.clear();          for (int i = height.length - 1; i > -1; i--) {              while (!smallStack.isEmpty() && smallStack.peek().height >= height[i]){                smallStack.pop();            }            if (!smallStack.isEmpty()) {                rightSmall[i] = smallStack.peek().pos;            }             else {                 rightSmall[i] = height.length ;             }            PositionNode newNode = new PositionNode(i,height[i]);            smallStack.push(newNode);        }        int maxArea = 0;        for (int i = 0; i < height.length; i++) {            int thisArea = height[i] * Math.abs(rightSmall[i] - leftSmall[i] - 1);            maxArea = Math.max(maxArea,thisArea);        }        return maxArea;    }    class PositionNode {        int pos;        int height;        public PositionNode(int pos, int height) {            this.pos = pos;            this.height = height;        }    }}