LintCode-三数之和

给出一个有n个整数的数组S，在S中找到三个整数a, b, c，找到所有使得a + b + c = 0的三元组。

class Solution {
public:
    /**
     * @param numbers: Give an array numbers of n integer
     * @return: Find all unique triplets in the array which gives the sum of zero.
     */
    vector<vector<int>> threeSum(vector<int> &numbers) {
        // write your code here
        vector<vector<int>> result;
        int i=0,j=0,k=0;
        int size = numbers.size();
        if (size < 3){
            return result;
        }
        sort(numbers.begin(), numbers.end());
        for(k = 0; k < size - 2 ;k++ ){
            if(k > 0 && numbers[k]==numbers[k-1]) {
                continue;
            }
            
            for(i = k+1,j = size-1;i<j;){
                if(i > k+1 && numbers[i]==numbers[i-1]) {
                    i++;
                    continue;
                }
                if(j<size-1 && numbers[j]==numbers[j+1]) {
                    j--;
                    continue;
                }
                int sum = numbers[i] + numbers[j] + numbers[k];
                if(sum == 0) {
                    vector<int> temp;
                    temp.push_back(numbers[k]);
                    temp.push_back(numbers[i]);
                    temp.push_back(numbers[j]);
                    result.push_back(temp);
                    i++;
                    j--;
                }else if(sum >0) {
                    j--;
                }else {
                    i++;
                }
            }
        }
         return result;
    }
};