Max rectangle in a histogram

maxrect.js

// o(n)
// https://stackoverflow.com/a/26202717
// read this: https://stackoverflow.com/a/50651622/336431
function getMaxRect(heights) {

  const stack = [];
  let max = 0;
  let i = 0;

  while (i < heights.length) {
    if (stack.length === 0 || (stack.length > 0 && heights[stack[stack.length - 1]] <= heights[i])) {
      stack.push(i++);
    } else {
      let top_area = heights[stack.pop()] * (stack.length === 0 ? i : (i - stack[(stack.length - 1)] - 1));
      max = Math.max(max, top_area)
    }
  }

  while (stack.length > 0) {
    let top_area = heights[stack.pop()] * (stack.length === 0 ? i : (i - stack[(stack.length - 1)] - 1));
    max = Math.max(max, top_area)
  }
  return max;
}