Based on:

We create a new loop:

class Solution {
public:
	vector<vector<int>> fourSum(vector<int>& nums, int target) {
		sort(nums.begin(), nums.end());
		vector<vector<int>> res;
		int T, S, r, l;
		for (int i = 0; i < nums.size(); ++i) {
			if (i > 0 && nums[i] == nums[i - 1]) {
				continue;
			}
			for (int j = i + 1; j < nums.size(); ++j) {
				if (j > i + 1 && nums[j] == nums[j - 1]) {
					continue;
				}
				l = j + 1;
				r = nums.size() - 1;
				T = target - nums[i] - nums[j];
				while (l < r) {
					S = nums[l] + nums[r];
					if (S == T) {
						res.push_back({nums[i], nums[j], nums[l], nums[r]});
						while (l < r && nums[l] == nums[l + 1]) {
							l++;
						}
						while (l < r && nums[r] == nums[r - 1]) {
							r--;
						}
						l++;
						r--;
					} else if (S < T) {
						l++;
					} else {
						r--;
					}
				}
			}
		}
		return res;
	}
};