Convert a String to Float

Code

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

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

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

    // Parse characters
    for (; str[i] != '\0'; i++) {
        if (str[i] == '.') {
            inFraction = 1;
            continue;
        }
        if (str[i] >= '0' && str[i] <= '9') {
            if (!inFraction) {
                result = result * 10 + (str[i] - '0');
            } else {
                fraction = fraction * 10 + (str[i] - '0');
                divisor *= 10;
            }
        } else {
            // Invalid character handling (optional)
            break;
        }
    }

    result = result + fraction / divisor;
    return result * sign;


}

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