CSCI151 L21 P2

#include <stdio.h>
#include <string.h>
#include <math.h>

double strToDouble(char str[]){
    int i=0;
    double result=0;
    int p=0;
    _Bool negativeSignP=0;
    _Bool negativeSignN=0;
    if (str[i]=='-'){
        negativeSignN=1;
        i++;
    }
    for ( ; str[i]>='0' && str[i]<='9'; i++){
        result=result*10+str[i]-'0';
    }
    if (str[i]=='.'){
        int k=10;
        i++;
        for ( ; str[i]>='0' && str[i]<='9'; i++, k*=10){
            result=result+(double)(str[i]-'0')/k;
        }
    }
    if (str[i]=='e'){
        i++;
        if (str[i]=='-'){
            negativeSignP=1;
            i++;
        }
        for ( ; str[i]>='0' && str[i]<='9'; i++){
            p=p*10+str[i]-'0';
        }
        int j;
        for (j=0; j<p; j++){
            if (negativeSignP)
                result/=10.0;
            else
                result*=10.0;
        }
    }
    if (negativeSignN){
        result*=(-1);
    }
    return result;
}

int main(void) {
    char n[50];
    scanf("%s", n);
    printf("%f", strToDouble(n));
    return 0;
}