PAT 1073 Scientific Notation

#include <cstdio>

#include <cstdlib>



using namespace std;





int str2num(const char* str) {

    int v = 0;

    int i = 0;

    while (str[i] != '\0') {

        v = v * 10 + str[i] - '0';

        i++;

    }

    

    return v;

}



int main() {

    int esign= 1;

    int exp = 0;

    char int_part = '0';

    char fra_part[10009];

    char ch;

    // read sign

    scanf("%c", &ch);

    if (ch == '-') {

        printf("%c", ch);

    }

    // read int part number, 1digit

    scanf("%c", &int_part);

    

    // skip dot

    scanf("%c", &ch);

    

    // read fra part

    int fra_len = 0;

    while (true) {

        scanf("%c", &ch);

        if (ch == 'E') break;

        fra_part[fra_len++] = ch;

    }

    fra_part[fra_len] = '\0';

    

    // read exp sign

    scanf("%c", &ch);

    if (ch == '-') esign = -1;

    

    char buf[10000];

    scanf("%s", buf);

    exp = str2num(buf);

    

    if (esign >= 0 || exp == 0) {

        printf("%c", int_part);

        if (exp < fra_len) {

            for (int i=0; i<exp; i++) {

                printf("%c", fra_part[i]);

            }

            printf(".");

            for (int i=exp; i<fra_len; i++) {

                printf("%c", fra_part[i]);

            }

        } else {

            for (int i=0; i<fra_len; i++) {

                printf("%c", fra_part[i]);

            }

            for (int i=fra_len; i<exp; i++) {

                printf("0");

            }

        }

    } else {

        printf("0.");

        for (int i=1; i<exp; i++) {

            printf("0");

        }

        printf("%c", int_part);

        for (int i=0; i<fra_len; i++) {

            printf("%c", fra_part[i]);

        }

    }

    

    return 0;

}

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