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();};复制代码

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。