和为s的连续正数序列

剑指offer刷题系列：

面试题57 - II. 和为s的连续正数序列

暴力解法：
针对每种解法检查是否可以等于target

/**
 * @param {number} target
 * @return {number[][]}
 */
var findContinuousSequence = function(target) {
    if(target<3) {
        return [];
    }

    let max = Math.ceil(target/2);
    let res = [];
    for(let i = 1; i < max; i++) {
        for(let j = i+ 1; j <= max; j++) {
            let sum = (i+j)*(j-i+1)/2;
            if(sum === target) {
                res.push(get(i, j));
            }
        }
    }
    return res;
};
function get(i, j) {
    let res = [i];
    let val = i; 
    while(val < j) {
        res.push(val+1);
        val++;
    }
    return res;
}

结果超出了时间限制

改用双指针，滑动窗口

/**
 * @param {number} target
 * @return {number[][]}
 */
var findContinuousSequence = function(target) {
    if(target<3) {
        return [];
    }
    let p = 1;
    let q = 2;
    let max = Math.ceil(target/2);
    let res = [];
    while(p < max && q <= max) {
        let sum = (p+q)*(q-p+1)/2;
        if(sum === target) {
            res.push(get(p, q));
            p++;
        } else if(sum < target) {
            q++;
        } else {
            p++;
        }
    }
    return res;
};
function get(i, j) {
    let res = [i];
    let val = i; 
    while(val < j) {
        res.push(val+1);
        val++;
    }
    return res;
}

关于滑动窗口，这里有篇文章讲的挺清晰的，可以参考一下：
https://zhuanlan.zhihu.com/p/107786714?utm_source=wechat_session&utm_medium=social&utm_oi=1047235829767958528