15. 三数之和（算法200题-36）

/**
 * @param {number[]} nums
 * @return {number[][]}
 * [-4,-1,-1,0,1,2]
 */
var threeSum = function (nums) {
    const list = []
    if (nums.length < 3) return []
    nums.sort((a, b) => a - b)
    for (let i = 0; i < nums.length; i++) {
        if(nums[i] ===nums[i - 1]) {
            continue
        }
        let left = i + 1,
            right = nums.length - 1
        while (right > left) {
            if (right === i) {
                right--
            } else if (nums[left] + nums[right] + nums[i] === 0) {
                list.push([nums[left], nums[right], nums[i]])
                while (nums[left] === nums[left + 1]) {
                    left++
                }
                left++
                while (nums[right] === nums[right + 1]) {
                    right--
                }
                right--
            } else if (nums[left] + nums[right] + nums[i] < 0) {
                left++
            } else {
                right--
            }
        }
    }
    return list
};