题解 | #数组中相加和为0的三元组#

class Solution { public: vector<vector > threeSum(vector &num) { if (num.empty()) return {};

    vector<vector<int> > res;
    std::sort(num.begin(), num.end());
    int i = 0, j = 1;
    int k = num.size() - 1;
    int prei = INT_MAX;
    
    for (; i < num.size(); i++) {
        if (num[i] > 0) break;
        if (prei == num[i]) continue;
        prei = num[i];
        
        j = i+1;
        k = num.size() - 1;
        
        while (j < k) {
            if (num[i] + num[j] > 0) break;
            if (num[k] < 0) break;
            
            int tmp = num[i] + num[j] + num[k];
            if (0 == tmp) {
                res.push_back({num[i], num[j],num[k]});
                
                ++j, --k;
                while (j < k && num[j] == num[j-1]) ++j;
                while (j < k && num[k] == num[k+1]) --k;
            } else if (tmp > 0) {
                k--;
            } else {
                j++;
            }
        }
        
    }
    
    return res;
}

};