const arr = [1,5,2,9,7,6]
/**
1 5 9 7 2 6

l = 1
r = 4
1,5,2,9,7,6
2 odd ? l++
2 even ? r--
else : l
 */

let left = 0
let right = arr.length - 1

while(left < right){
  if(arr[left] % 2 == 1 && arr[right] % 2 == 1){
    left++
  }else if(arr[left] % 2 == 0 && arr[right] % 2 == 0){
    right--
  }else{
   if(arr[left] % 2 != 1 && arr[right] % 2 != 0){
     let temp = arr[right]
        arr[right] = arr[left]
        arr[left] = temp
      }
      left++
      right--
  }
}

console.log(arr)