1323. Maximum 69 Number

Maximum69Number.cs

public class Solution {
  public int Maximum69Number (int num) {
    var numBase = (int)Math.Log(num, 10);
    var div = (int)Math.Pow(10, numBase);
    var maxNumber = 0;
    var flipped = false;
    while(num > 0){
      var digit = num / div;
      num = num - (digit * div);
      if(digit == 6 && !flipped){
        flipped = true;
        digit = 9;
      }
      maxNumber += digit * div;
      div /= 10;
    }

    return maxNumber;
  }
}