leetcode18-四数之和

leetcode 18

思路

参考三数之和，四数之和在三数之和外再套一层循环，然后里面内容跟三数之和一致，去重逻辑也一致

实现

var fourSum = function (nums, target) {
    nums.sort((a, b) => a - b);
    let result = [];
    for (let i = 0; i < nums.length - 3; i++) {
        if (i > 0 && nums[i] === nums[i - 1]) continue;
        for (let j = i + 1; j < nums.length - 2; j++) {
            if (j > i + 1 && nums[j] === nums[j - 1]) continue;
            let left = j + 1, right = nums.length - 1;
            while (left < right) {
                if (left > j + 1 && nums[left] === nums[left - 1]) {
                    left++;
                    continue;
                }
                if (right > nums.length - 1 && nums[right] === nums[right - 1]) {
                    right--;
                    continue;
                }
                const sum = nums[i] + nums[j] + nums[left] + nums[right];
                if (sum === target) {
                    result.push([nums[i], nums[j], nums[left], nums[right]]);
                    left++;
                } else if (sum < target) {
                    left++;
                } else {
                    right--;
                }
            }
        }
    }
    return result;
};