(Algorithms in Javascript) Leetcode 15. 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.

leetcode-15-three-sum-to-zero-1.js

const threeSum = (nums) => {
  let len = nums.length;
  if(len < 3) return [];
  nums.sort(function(a,b){
    return a-b;
  })
  if(nums[0] > 0 || nums[0] + nums[1] + nums[2] > 0) return [];
  if(len === 3) {
    if(nums[0] + nums[1] + nums[2] === 0) return [nums];
    else return [];
  }
  //console.log(nums);
  
  let result = [];
  let checker = '';
  
  for(let i=0; i<len; i++){
    var sum = -nums[i];
    for(let j=i+1, k = len - 1; j<k;){
      //console.log(i + ', ' + j + ', ' + k + ': ' + nums[i] + ', ' + nums[j] + ', ' + nums[k]);
      var temp = nums[j] + nums[k];
      if(temp < sum){
        j++;
      } else if(temp > sum){
        k--;
      } else {
        var triplet =  [nums[i], nums[j], nums[k]];
        result.push(triplet);
        
        //skip j term if it's a duplicate
        while(nums[j] === nums[j+1] && j<len) j++;
        //skip k term if it's a duplicate
        while(nums[k] === nums[k-1] && k>0) k--;
        j++;
        k--;
      }
    }
    //skip i term if it's a duplicate
    while(nums[i] === nums[i+1] && i<len) i++;
  }
  
  return result;
};