LeetCode 42 javascript解决方案

思路

代码

/**
 * @param {number[]} height
 * @return {number}
 */
var trap = function(height) {
    function cutUselessInTheSides(list = height){
        let p = 0;
        while((p < list.length - 1) && (list[p] <= list[p + 1])){
            p++;
        }
        list = list.slice(p);
        p = list.length - 1;
        while((p > 0) && (list[p - 1] >= list[p])){
            p--;
        }
        list = list.slice(0, p + 1);
        return list;
    }
    function calSum(list){
        let max = Math.min(list[0], list[list.length - 1]);
        let sum = 0;
        for(let i = 0; i < list.length; ++i){
            let delta = max - list[i];
            sum += (delta > 0 ? delta : 0);
        }
        return sum;
    }
    function calculator(list = height, total = 0){
        if(list.length < 3){
            return total;
        }
        list = cutUselessInTheSides(list);
        if(list.length < 3){
            return total;
        }

        let firstBiggerIndex = -1;
        for(let i = 1; i < list.length; ++i){
            if(list[i] >= list[0]){
                firstBiggerIndex = i;
                break;
            }
        }
        if(firstBiggerIndex >= 0){ // 找到了
            let leftList = list.slice(0, firstBiggerIndex + 1);
            total += calSum(leftList);
            list = list.slice(firstBiggerIndex);
            return calculator(list, total);
        }
        // 从右往左找
        for(let i = list.length - 2; i >= 0; --i){
            if(list[i] >= list[list.length - 1]){
                firstBiggerIndex = i;
                break;
            }
        }
        if(firstBiggerIndex >= 0){ // 找到了
            let rightList = list.slice(firstBiggerIndex);
            total += calSum(rightList);
            list = list.slice(0, firstBiggerIndex + 1);
            return calculator(list, total);
        }
        else{
            return total;
        }
    }
    return calculator();
};

感想

这题我刷了一个多月，思路还是睡觉的时候想到的，虽然很早就想到了解决思路，每次下手都觉得麻烦 就拖到现在，没想到一次性提交成功了，效率也超过了一半以上的提交，很开心。