leetcode刷题系列C++-3sum

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Note:

• Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c)
• The solution set must not contain duplicate triplets.

    For example, given array S = {-1 0 1 2 -1 -4},    A solution set is:    (-1, 0, 1)    (-1, -1, 2)

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class Solution {public:    vector<vector<int>> threeSum(vector<int>& nums) {        vector<vector<int> > result;        if(nums.size() < 3)            return result;        sort(nums.begin(),nums.end());        const int target = 0;        for(auto a = nums.begin(); a < prev(nums.end(),2); ++a)        {            auto b = next(a);            if(a != nums.begin() && *a == *(prev(a)))                continue;            auto c = prev(nums.end());            while(b < c)            {                if(*a + *b + *c < target)                {                    ++b;                }                else if(*a + *b + *c > target)                {                    --c;                }                else                {                    result.push_back({*a,*b,*c});                    ++b;                    --c;                }            }        }        //sort(result.begin(),result.end());        result.erase(unique(result.begin(),result.end()),result.end());        return result;    }};