PlusOne.java

public class Solution {
 public int[] plusOne(int[] digits) {
 
 int carry = 1;//The initial one to be added to the array.
 for(int i = digits.length - 1; i >= 0; --i){
 int temp = digits[i] + carry;//Add one.
 carry = temp / 10;//Do we need to carry the one? 
 digits[i] = temp % 10;//set new digit.
 }
 
 if(carry == 1){// this is in the event that we have to carray a one at the head of the array so we need an array of one size bigger
 int[] newArray = new int[digits.length + 1];
 newArray[0] = 1;//Set leading digit to one.
 for(int i = 0; i < digits.length; i++){
 newArray[i+1] = digits[i];
 }
 return newArray;
 }
 return digits;
 }
}