pairSumInDifferentApproaches

let data = [1, 2, 3, 5, 7],
    sum = 18;

function nSquare() {
  let result = false;
    for(let i=0;i<data.length;i++){
      for(let j=i+1;j<data.length;j++){
        if(data[i] + data[j] === sum){
          result = true;
          break;
        }
      }
      if(result===true)break;
    }
    if (result === true) return "YES";
    return "NO";
}

function nLogN() {
  let result = false;
  let newArray = [...data];
  newArray.sort();
  let l =0, r = newArray.length-1;
  while(l<r){
    let cSum = newArray[l] + newArray[r] ;
    if(cSum === sum){
      result = true;
      break;
    }
    if(cSum<sum)l++;
    else r--;
  }
  if (result === true) return "YES";
  return "NO";
}

function orderN(){
  let result = false;
  let map = [];
  for(let i=0;i<data.length;i++){
    if(map[data[i]]){
      result = true;
      break;
    }
    map[sum-data[i]]=true;
  }
  if (result === true) return "YES";
  return "NO";
}


console.log(nSquare());
console.log(nLogN());
console.log(orderN());