15. 三數之和(雙指標)
阿新 • • 發佈:2021-06-27
給你一個包含 n 個整數的陣列nums,判斷nums中是否存在三個元素 a,b,c ,使得a + b + c = 0 ?請你找出所有和為 0 且不重複的三元組。
注意:答案中不可以包含重複的三元組。
示例 1:
輸入:nums = [-1,0,1,2,-1,-4]
輸出:[[-1,-1,2],[-1,0,1]]
示例 2:
輸入:nums = []
輸出:[]
示例 3:
輸入:nums = [0]
輸出:[]
提示:
0 <= nums.length <= 3000
-105 <= nums[i] <= 105
來源:力扣(LeetCode)
連結:https://leetcode-cn.com/problems/3sum
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class Solution { public: vector<vector<int>> threeSum(vector<int>& nums) { int len = nums.size(); vector<vector<int>> res; if(len < 3) { return res; } sort(nums.begin(), nums.end()); const int target = 0; for(int first = 0; first< len; first++) { if(first > 0 && nums[first] == nums[first-1]) { continue; } int third = len-1; for(int second = first +1; second < third; second++) { if(second > first+1 && nums[second] == nums[second - 1]) { continue; } while(third > second && nums[first] + nums[second] + nums[third] > target) { third--; } if(second < third && (nums[first] + nums[second] + nums[third] == 0)) { vector<int> tmp ; tmp.push_back(nums[first]); tmp.push_back(nums[second]); tmp.push_back(nums[third]); res.push_back(tmp); } } } return res; } };