> For the complete documentation index, see [llms.txt](https://mayanktyagi3111.gitbook.io/interview-prep/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mayanktyagi3111.gitbook.io/interview-prep/strings-arrays-and-2-pointers/add-one-to-number.md).

# Add One To Number

Given a non-negative number represented as an array of digits,

add 1 to the number ( increment the number represented by the digits ).

The digits are stored such that the most significant digit is at the head of the list.

**Example:**

If the vector has `[1, 2, 3]`

the returned vector should be `[1, 2, 4]`

as `123 + 1 = 124`.

> **NOTE:** Certain things are intentionally left unclear in this question which you should practice asking the interviewer.\
> For example, for this problem, following are some good questions to ask :
>
> * **Q :** Can the input have 0’s before the most significant digit. Or in other words, is `0 1 2 3` a valid input?
> * **A :** For the purpose of this question, **YES**
> * **Q :** Can the output have 0’s before the most significant digit? Or in other words, is `0 1 2 4` a valid output?
> * **A :** For the purpose of this question, **NO**. Even if the input has zeroes before the most significant digit.

```java
public class Solution {
    public ArrayList<Integer> plusOne(ArrayList<Integer> A) {
        ArrayList<Integer> t=new ArrayList<>();
        int carry=1;
        for(int j=A.size()-1;j>=0;j--){
            int num=A.get(j)+carry;
            carry=num/10;
            num=num%10;
            t.add(0,num);
        }
        if(carry==1){
            t.add(0,1);
        }
        ArrayList<Integer> ans=new ArrayList<>();
        boolean flag=true;
        for(int i=0;i<t.size();i++){
            if(flag && t.get(i)==0){
                
            }
            else{
                flag=false;
                ans.add(t.get(i));
            }
        }
        return ans;
    }
}

```