Function trap

javascript/0042-trapping-rain-water.js:9–40

(height)

 *
 */
var trap = function (height) {
    const maxLeft = [];
    const maxRight = [];
    const minLeftRight = [];

    let current = 0;
    for (let i = 0; i < height.length; i++) {
        maxLeft.push(current);
        current = Math.max(current, height[i]);
    }
    current = 0;
    for (let i = height.length - 1; i > -1; i--) {
        maxRight.push(current);
        current = Math.max(current, height[i]);
    }
    // because the elements were added reverse.
    maxRight.reverse();

    for (let i = 0; i < height.length; i++) {
        const minofLeftRight = Math.min(maxLeft[i], maxRight[i]);
        minLeftRight.push(minofLeftRight);
    }

    let water = 0;
    for (let i = 0; i < height.length; i++) {
        if (minLeftRight[i] - height[i] > 0) {
            water += minLeftRight[i] - height[i];
        }
    }

    return water;
};

/**
 * https://leetcode.com/problems/trapping-rain-water/