02-1-multiple_Pointer-PATTERN_sum_zero.js

//write a function called sumZero which accepts a sorted array of integers. The function should find the first pair where the sum is 0. Return an array that includes both values that sum to zero or undefined if a pair does not exist. 

//Time Complexity O(N)
//Space Complexity O(1)

const sumZero = (arr) => {

    let left = 0;
    let right = arr.length -1;
  
    while(left < right){
      
      console.log("left", arr[left])
      console.log("right", arr[right])
  
      let sum = arr[left] + arr[right]
      
      if(sum === 0){
        return [arr[left], arr[right]]
      } else if(sum > 0){
        right--
      } else {
        left++
      }
    }
  }
  
  sumZero([-4, -3, -2, -1, 0, 1, 2, 3, 10])
  


///naive approach. nested loop. 
function sumZero(arr){
    for(let i = 0; i < arr.length; i++){
        for(let j = i+1; j < arr.length; j++){
            if(arr[i] + arr[j] === 0){
                console.log(arr[i], arr[j])
                return [arr[i], arr[j]];
            }
        }
    }
}

sumZero([-4,-3,-2,-1,0,1,2,5])