代码随想录：四数之和

代码随想录：四数之和

就是三数之和

class Solution {
public:
    vector<vector<int>> fourSum(vector<int>& nums, int target) {
        vector<vector<int>> res;
        if (nums.size() < 4)
            return res;
        sort(nums.begin(), nums.end());
        for (int i = 0; i < nums.size() - 3; i++) {
            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }
            for (int j = i + 1; j < nums.size() - 2; j++) {
                if (j > i + 1 && nums[j] == nums[j - 1]) {
                    continue;
                }
                int left = j + 1;
                int right = nums.size() - 1;
                while (left < right) {
                    if ((long)nums[i] + nums[j] + nums[left] + nums[right] ==
                        target) {
                        res.push_back(
                            {nums[i], nums[j], nums[left], nums[right]});
                        left++;
                        right--;
                        while (left < right && nums[left] == nums[left - 1]) {
                            left++;
                        }
                        while (left < right && nums[right] == nums[right + 1]) {
                            right--;
                        }

                    } else if ((long)nums[i] + nums[j] + nums[left] +
                                   nums[right] <
                               target) {
                        left++;
                    } else if ((long)nums[i] + nums[j] + nums[left] +
                                   nums[right] >
                               target) {
                        right--;
                    }
                }
            }
        }
        return res;
    }
};