【leetCode】18_四數之和
阿新 • • 發佈:2018-12-14
雙指標法。
class Solution { public: vector<vector<int>> fourSum(vector<int>& nums, int target) { vector<vector<int>> ans; sort(nums.begin(), nums.end()); for (int i = 0; i < nums.size(); i ++){ for (int j = nums.size() - 1; j > i; j --){ int l = i + 1, r = j - 1; int t = target - nums[i] - nums[j]; while (l < r){ if (nums[l] + nums[r] < t) l ++; else if (nums[l] + nums[r] > t) r --; else{ vector<int> t = {nums[i], nums[l], nums[r], nums[j]}; ans.push_back(t); while (l < r && nums[l + 1] == nums[l]){ l ++; } l ++; while (l < r && nums[r - 1] == nums[r]){ r --; } r --; } } while(nums[j - 1] == nums[j] && j > i){ j --; } } while (nums[i + 1] == nums[i]){ i ++; } } return ans; } };