LC 15. 三数之和 - 《leetcode》

代码 :

class Solution {
public:
    vector<vector<int>> res;
    vector<vector<int>> threeSum(vector<int>& nums) {
        if(nums.size() < 3) return res; 
        sort(nums.begin(), nums.end()); 
        for(int i = 0; i < nums.size() - 2; i ++ ) {
            if(i > 0 && nums[i] == nums[i - 1]) 
                continue; // repeat
            for(int j = i + 1, k = nums.size() - 1; j < k; j ++ ) {
                if (j > i + 1 && nums[j] == nums[j - 1]) 
                    continue; // repeat
                // a b c d e => a + b + d == 0 => k points to d
                while(j < k && nums[i] + nums[j] + nums[k] > 0) {
                    k -- ; 
                }
                if(j == k) continue;
                if(nums[i] + nums[j] + nums[k] == 0) 
                    res.push_back({nums[i], nums[j], nums[k]});
            }
        }
        return res; 
    }
};

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class Solution {
public:
    vector<vector<int>> res;
    vector<vector<int>> threeSum(vector<int>& nums) {
        if(nums.size() < 3) return res; 
        sort(nums.begin(), nums.end()); 
        for(int i = 0; i < nums.size() - 2; i ++ ) {
            if(i > 0 && nums[i] == nums[i - 1]) 
                continue; // repeat
            for(int j = i + 1, k = nums.size() - 1; j < k; j ++ ) {
                if (j > i + 1 && nums[j] == nums[j - 1]) 
                    continue; // repeat
                // a b c d e => a + b + d == 0 => k points to d
                while(j < k - 1 && nums[i] + nums[j] + nums[k - 1] >= 0) {
                    k -- ; 
                }
                if(nums[i] + nums[j] + nums[k] == 0) 
                    res.push_back({nums[i], nums[j], nums[k]});
            }
        }
        return res; 
    }
};