LeeCode 3Sum

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

Note:

The solution set must not contain duplicate triplets.

Example:

Given array nums = [-1, 0, 1, 2, -1, -4],

A solution set is:
[
  [-1, 0, 1],
  [-1, -1, 2]
]

class Solution {
public:
    vector<vector<int>> threeSum(vector<int>& nums) {
        int cnt = nums.size();
        vector<vector<int>> rlt;
        sort(nums.begin(), nums.end());
        for(int i=0; i<=cnt-3; i++) {
            if(i>0 && nums[i]==nums[i-1]) continue;
            int b = i+1, c = cnt-1;
            while(b<c) {
                int sum = nums[i]+nums[b]+nums[c];
                if(sum > 0) {
                    c--;
                }
                else if(sum < 0) {
                    b++;
                }
                if(sum == 0) {
                    rlt.push_back({nums[i], nums[b], nums[c]});
                    while(b<c && nums[b]==nums[b+1]) b++;
                    while(b<c && nums[c]==nums[c-1]) c--;
                    b++;
                    c--;
                }
            }
        }
        return rlt;
    }
};