Problem of the Day -- Atoi

Atoi

Today's Problem of the Day is to reimplement a classic function, atoi. Atoi takes in one parameter, a string, and returns an int version of that string. So when passed the string "10" atoi will return 10. If the string can't be converted to an int just return 0 or throw an error.

Permalink: http://problemotd.com/problem/atoi/

Comments:

Anonymous - 10 years, 4 months ago
In Ruby this is trivial:
```
def atoi(an_object)
  an_object.to_i
end
```
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David - 10 years, 3 months ago

An Atoi by any other name is still Atoi.

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Dustin S. - 10 years, 4 months ago

I wrote this in Java, but, this could be a general language implementation. Sorry the indentation is weird.

private static final int ASCII_ZERO = 48;

public int atoi(String s) throws Exception {
    if (s == null) {
        throw new NullPointerException("String can't be null.");
    }
    int total = 0;
    int s_len = s.length();
    for (int i = s_len - 1; i >= 0; i--) {
        int c = s.charAt(i);
        double power = Math.pow(10, s_len - 1 - i);
        if (c == ASCII_ZERO) {
           continue;
        } else if (c > ASCII_ZERO && c <= (ASCII_ZERO + 9) {
           total += (power * (c - ASCII_ZERO));
        } else {
           throw new Exception("Invalid character.");
        }
    }
    return total;
}

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Dustin S. - 10 years, 4 months ago
Sorry, I should have put double power = Math.pow(10, s_len -1 - i); in the else-if block.

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bumbleguppy - 10 years, 3 months ago

javascript also has the native parseInt() function, but here's my effort:

function parseIntRedeaux(input_string){
    var resultInt = 0;
    var digitString = '0123456789';
    var digit = 0;
    var power = 1;
    var i = 0;
    if(typeof input_string === 'string' && input_string.length > 0){
        i = input_string.length;
        while(i--){
            digit = digitString.indexOf(input_string.charAt(i));
            if(digit > -1){
                resultInt += (digit * power);
            }else{
                throw new Error('Input contains non-numerical characters');
            }
            power *= 10;
        }
        return resultInt;
    }else{
        throw new Error('Input must be string of non-zero length');
    }
}

console.log(parseIntRedeaux('a1234'));

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Aaron Frase - 10 years, 3 months ago

Here's my implementation in python without using int().

def atoi(n):
    num_con = {'0': 0, '1': 1, '2': 2, '3': 3,
               '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9}
    try:
        s_len = len(n)
        ret = 0
        for x in n:
            ret += num_con[x] * 10 ** (s_len - 1)
            s_len -= 1
        return ret
    except:
        return 0

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Problem of the Day A new programming or logic puzzle every Mon-Fri

Atoi

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Problem of the Day
A new programming or logic puzzle every Mon-Fri