Given an array nums of n integers and an integer target, are there elements a, b, c, and d in nums such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.
Note:
The solution set must not contain duplicate quadruplets.
Example:
Given array nums = [1, 0, -1, 0, -2, 2], and target = 0.
A solution set is:
[
[-1, 0, 0, 1],
[-2, -1, 1, 2],
[-2, 0, 0, 2]
]
1 class Solution { 2 public: 3 vector<vector<int>> fourSum(vector<int>& nums, int target) { 4 int size = nums.size(); 5 sort(nums.begin(), nums.end()); 6 vector<vector<int>> ans; 7 for (int i = 0; i < size; i++) { 8 if (i > 0 && nums[i] == nums[i - 1])continue; 9 for (int j = i + 1; j < size - 2; j++) { 10 if (j > i + 1 && nums[j] == nums[j - 1])continue; 11 int p = j + 1, q = size - 1; 12 int res = target - nums[i] - nums[j]; 13 while (p < q) { 14 int tmp = nums[p] + nums[q]; 15 if (tmp < res)p++; 16 else if (tmp == res) { 17 vector<int> tt; 18 tt.push_back(nums[i]); 19 tt.push_back(nums[j]); 20 tt.push_back(nums[p]); 21 tt.push_back(nums[q]); 22 ans.push_back(tt); 23 while (nums[p + 1] == nums[p])p++; 24 while (nums[q - 1] == nums[q])q--; 25 p++, q--; 26 } 27 else q--; 28 } 29 } 30 } 31 return ans; 32 } 33 };
跟3sum基本相同