思路：
设置 i j k n 四个游标，思想如同三数之和
# include<iostream> # include<vector> # include<string> # include<algorithm> # include<math.h> # include<climits> using namespace std; vector<vector<int>> fourSum(vector<int>& nums, int target) { int i=0, j, k, n; int size = nums.size(); vector<vector<int>>res; sort(nums.begin(), nums.end());//将nums有序化 while (i < size - 3) {//i的活动范围 j = i + 1; while (j < size - 2) {//j的活动范围 k = j + 1; n = size - 1; while (k < n) { if ((nums[i] + nums[j] + nums[k] + nums[n]) > target) { n--; while (k < n && nums[n] == nums[n + 1])n--; } else if ((nums[i] + nums[j] + nums[k] + nums[n]) < target) { k++; while (k < n && nums[k] == nums[k - 1])k++; } else {//与target一致 res.push_back({ nums[i] , nums[j] , nums[k] , nums[n] });//将此数组入vector k++; while (k < n && nums[k] == nums[k - 1])k++; n--; while (k < n && nums[n] == nums[n + 1])n--; } }//k<n的循环 j++; while (j < size - 2 && nums[j] == nums[j - 1])j++; } i++; while (i < size - 3 && nums[i] == nums[i - 1])i++; } return res; } int main(void) { vector<int> nums; nums.push_back(-3); nums.push_back(-2); nums.push_back(-1); nums.push_back(0); nums.push_back(0); nums.push_back(1); nums.push_back(2); nums.push_back(3); vector<vector<int>>res; res = fourSum(nums, 0); for (int i = 0; i < res.size(); i++) { for (int j = 0; j < res[i].size(); j++) { cout << res[i][j] << " "; } cout << endl; } return 0; }
