# 02. Implement Atoi

The problem can be found at the following link: [Question Link](https://www.geeksforgeeks.org/problems/implement-atoi/1)

## My Approach

I have implemented the Atoi function using a simple iteration through the input string. Here's a breakdown of the steps:

1. Initialize a variable `n` to store the converted integer.
2. Iterate through the characters of the string.
   * If it's the first character and it's a '-', skip it since it represents a negative number.
   * If the character is a digit, update `n` by multiplying it by 10 and adding the digit.
   * If the character is not a digit, return -1 as the input is invalid.
3. Return the final integer, considering the sign.

## Time and Auxiliary Space Complexity

* **Time Complexity**: O(N), where N is the length of the input string. We iterate through the string once.
* **Auxiliary Space Complexity**: O(1), as we use a constant amount of space for variables.

## Code (C++)

```cpp
class Solution {
public:
    int atoi(string s) {
        int n = 0; 
        for (int i = 0; i < s.length(); i++) {
            if (i == 0 && s[i] == '-') 
                continue;
            if (s[i] >= '0' && s[i] <= '9')
                n = n * 10 + s[i] - '0';
            else 
                return -1; 
        }
        return (s[0] == '-') ? -n : n;
    }
};
```

## Contribution and Support

For discussions, questions, or doubts related to this solution, please visit our [discussion section](https://github.com/getlost01/gfg-potd/discussions). We welcome your input and aim to foster a collaborative learning environment.

If you find this solution helpful, consider supporting us by giving a `⭐ star` to the [getlost01/gfg-potd](https://github.com/getlost01/gfg-potd) repository.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://gl01.gitbook.io/gfg-editorials/2024/02-2024-feb-1/02-implement-atoi.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.