Solution for Trapping RainWater Problem

trapping-rainwater.js

var trap = function(height) {
    
    let left_max = [];
    let right_max = [];
    let rainWaterUnits = 0;
    let n = height.length;
    
    left_max[0] = height[0]
    for(let i=1;i<n;i++) {
        left_max[i] = Math.max(height[i], left_max[i-1]);
    }
    
    right_max[n-1] = height[n-1];
    for(let i = n-2; i>=0; i--) {
        right_max[i] = Math.max(height[i], right_max[i+1]);
    }
    
    for(let i=0;i<height.length;i++) {
        rainWaterUnits = rainWaterUnits + (Math.min(left_max[i], right_max[i]) - height[i]);
    }
    
    return rainWaterUnits;
    
};