maxSquareWithinHistoragram.js

function maxSquareWithinHistoragram(historagram) {
    let maxArea = 0;
    const barStack = [];
    let i = 0;
    while (i < historagram.length) {
        if (!barStack.length || historagram[barStack[barStack.length - 1]] <= historagram[i]) {
            barStack.push(i);
            i++;
        } else {
            const currentHeight = historagram[barStack.pop()];
            const currentWidth = !barStack.length ? i : i - 1 - barStack[barStack.length - 1];
            const area = currentHeight * currentWidth;
            if (area > maxArea) {
                maxArea = area;
            }
        }
    }
    while (barStack[barStack.length - 1]) {
        const currentHeight = historagram[barStack.pop()];
        const currentWidth = !barStack.length ? i : i - 1 - barStack[barStack.length - 1];
        const area = currentHeight * currentWidth;
        if (area > maxArea) {
            maxArea = area;
        }
    }
    return maxArea;
}

const historagramSample = [5, 3, 4, 4, 1, 9];
console.log(maxSquareWithinHistoragram(historagramSample)); // 12