剑指offer Two Pointers

剑指offer-和为s的连续正数序列

Posted by franki on May 21, 2021

和为s的连续正数序列

输入一个正整数 target ，输出所有和为 target 的连续正整数序列（至少含有两个数）。

序列内的数字由小到大排列，不同序列按照首个数字从小到大排列。

示例

输入：target = 9
输出：[[2,3,4],[4,5]]

思路

利用双指针，不断控制指针的移动，来收缩查找的范围，直到找到所有符合要求的结果

代码

/**
 * @param {number} target
 * @return {number[][]}
 */
var findContinuousSequence = function(target) {
    let mid = (1 + target) >> 1;
    let small = 1;
    let big = 2;
    const result = [];
    let curSum = small + big;
    while (small < mid) {
        if (curSum === target) {
            result.push(cal(small, big));
        }
        while(curSum > target && small < mid) {
            curSum -= small;
            small++;
            if (curSum === target) {
                result.push(cal(small, big));
            }
        }
        big++;
        curSum += big;
    }

    return result;
};

function cal(start, end) {
    const res = [];
    for (let i = start; i<=end; i++) {
        res.push(i);
    }
    return res;
}

复杂度分析:

  • 时间复杂度: O(N^2)
  • 空间复杂度：O(N)
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