leetcode-15-3sum

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        vector<vector<int>> res;
        vector<int> num;
        sort(nums.begin(), nums.end());
        for(int i = 0; i < nums.size(); i++)
        {
            int front = i+1;
            int end = nums.size() - 1;
            while(front < end)
            {
            	if(nums[i] + nums[front] + nums[end] == 0)
            	{
            		num.push_back(nums[i]);
            		num.push_back(nums[front]);
            		num.push_back(nums[end]);
            		res.push_back(num);
            		
                    
            		//Rolling the front pointer to the next different number forwards
            		while(front < end && nums[front] == num[1]) front++; 
            		
            		//Rolling the back pointer to the next different number backwards
            		while(front < end && nums[end] == num[2]) end--;
            		num.clear();
            	}
            	else if(nums[i] + nums[front] + nums[end] < 0) front++;
            	else end--;
            	
            	//过滤掉重复元素（过滤掉第一个相同的元素）
            	while(i+1 <= nums.size() && nums[i+1] == nums[i])
            	    i++;
            }
        }
        return res;
    }
};