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| 1 | +class Solution { |
| 2 | +public: |
| 3 | + vector<vector<int> > threeSum(vector<int> &num) { |
| 4 | + return threeSumGen(num, 0); |
| 5 | + } |
| 6 | + |
| 7 | + vector<vector<int> > threeSumGen(vector<int> &num, int target) { |
| 8 | + vector<vector<int>> allSol; |
| 9 | + if(num.size()<3) return allSol; |
| 10 | + sort(num.begin(),num.end()); |
| 11 | + |
| 12 | + for(int i=0; i<num.size()-2; i++) { |
| 13 | + if(i>0 && num[i]==num[i-1]) continue; // 去重 |
| 14 | + |
| 15 | + int left=i+1, right=num.size()-1; |
| 16 | + |
| 17 | + while(left<right) { |
| 18 | + int curSum = num[left]+num[right]; |
| 19 | + int curTarget = target-num[i]; |
| 20 | + if(curSum==curTarget) { |
| 21 | + vector<int> sol; |
| 22 | + sol.push_back(num[i]); |
| 23 | + sol.push_back(num[left]); |
| 24 | + sol.push_back(num[right]); |
| 25 | + allSol.push_back(sol); |
| 26 | + left++; |
| 27 | + right--; |
| 28 | + while(num[left]==num[left-1]) left++; |
| 29 | + while(num[right]==num[right+1]) right--; |
| 30 | + } |
| 31 | + else if(curSum<curTarget) |
| 32 | + left++; |
| 33 | + else |
| 34 | + right--; |
| 35 | + } |
| 36 | + } |
| 37 | + return allSol; |
| 38 | + } |
| 39 | + |
| 40 | + |
| 41 | + |
| 42 | +//backtrace TLE |
| 43 | + |
| 44 | +// vector<vector<int>> threeSum(vector<int>& nums) { |
| 45 | +// sort(nums.begin(), nums.end()); |
| 46 | +// if (nums.size() <= 2 || nums[0] > 0) return{}; |
| 47 | +// set<vector<int>> res; |
| 48 | +// for (int i = 0; i < nums.size(); i++) |
| 49 | +// { |
| 50 | +// int target = 0 - nums[i]; |
| 51 | +// int m = 0, n = nums.size() - 1; |
| 52 | +// while (m < n) |
| 53 | +// { |
| 54 | +// while (true) |
| 55 | +// { |
| 56 | +// if (m >= n) break; |
| 57 | +// if (m == i) |
| 58 | +// { |
| 59 | +// m++; |
| 60 | +// continue; |
| 61 | +// } |
| 62 | +// if (n == i) |
| 63 | +// { |
| 64 | +// n--; |
| 65 | +// continue; |
| 66 | +// } |
| 67 | +// if (nums[m] + nums[n] == target) { |
| 68 | +// vector<int> s = { nums[m++], nums[i], nums[n] }; |
| 69 | +// sort(s.begin(), s.end()); |
| 70 | +// res.insert(s); |
| 71 | +// break; |
| 72 | +// } |
| 73 | +// if (nums[m] + nums[n] > target) n--; |
| 74 | +// if (nums[m] + nums[n] < target) m++; |
| 75 | +// } |
| 76 | +// } |
| 77 | + |
| 78 | +// } |
| 79 | +// vector<vector<int>> fres(res.begin(), res.end()); |
| 80 | +// return fres; |
| 81 | +// } |
| 82 | +}; |
| 83 | + |
| 84 | +// accelerate the cin process. |
| 85 | +int x = []() { |
| 86 | + std::ios::sync_with_stdio(false); |
| 87 | + cin.tie(NULL); |
| 88 | + return 0; |
| 89 | +}(); |
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