LeetCode: Largest Rectangle in Histogram

LeetCode: Largest Rectangle in Histogram

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 LargestRectangleInHistogram {

public int largestRectangleArea(int[] height) {
if (height == null || height.length == 0) {
return 0;
}
Stack<Integer> stack = new Stack<Integer>();
int[] arr = Arrays.copyOf(height, height.length + 1);

int crt = 0;
int max = 0;
while (crt < arr.length) {
if (stack.isEmpty() || arr[crt] >= arr[stack.peek()]) {
stack.push(crt++);
} else {
int i = stack.pop();
max = Math.max(max, arr[i] * (stack.isEmpty() ? crt : crt - stack.peek() - 1));
}
}

return max;
}
}