https://leetcode.com/problems/3sum/

大事化小，小事化了

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/**
 * @param {number[]} nums
 * @return {number[][]}
 */
var threeSum = function(nums) {
    let res = []
    nums.sort((a, b) => a - b)
    if (nums.length < 3 || nums[0] > 0) {
        return res
    }
    for (let i = 0; i < nums.length - 2; i++) {
        if (i > 0 && nums[i] === nums[i - 1]) {
            continue
        }
        for (let j = i + 1, k = nums.length - 1; j < k;) {
            if (nums[i] + nums[j] + nums[k] === 0) {
                res.push([nums[i], nums[j], nums[k]])
                j++
                k--
                while (j < k && nums[j] === nums[j - 1]) {
                    j++
                }
                while (j < k && nums[k] === nums[k + 1]) {
                    k--
                }
            } else if (nums[i] + nums[j] + nums[k] > 0) {
                k--
            } else if (nums[i] + nums[j] + nums[k] < 0) {
                j++
            }
        }
    }
    return res
};