Convert a String to Float

Code

#include <stdio.h>
#include <stdint.h>

float custom_atof(const char *str)
{
    int i = 0;
    int sign = 1;
    float result = 0.0;
    float divisor = 10.0;

    if(str[i] == '-')
    {
        sign = -1;
        i++;
    }
    else if(str[i] == '+')
    {
        i++;
    }

    while(str[i] != '\0' && str[i] != '.')
    {
        result = result * 10 + (str[i] - '0');
        i++;
    }

    if(str[i] == '.')
    {
        i++;

        while(str[i] != '\0')
        {
            result += (str[i] - '0') / divisor;
            divisor *= 10;
            i++;
        }
    }

    return sign * result;
}

int main() {
    char str[101];
    fgets(str, sizeof(str), stdin);

    // Remove newline
    uint8_t i = 0;
    while (str[i]) {
        if (str[i] == '\n') {
            str[i] = '\0';
            break;
        }
        i++;
    }

    float value = custom_atof(str);
    printf("%.2f", value);
    return 0;
}

Solving Approach

 

 

 

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Input

123.45

Expected Output

123.45