Mon-1 Homework No.4

4-2.c

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

int main(){
    char buffer[100];
    int i, num, pow2 = 1, result=0;

    scanf("%99s", buffer);
    num = strlen(buffer);

    for(i=num-1;i>=0;i--){
        if(buffer[i] == '1')result += pow2;
        else if(buffer[i] != '0'){
            printf("Invalid Format.");
            return -1;
        }
        pow2 *= 2;
    }

    if(buffer[0] == '1')result = (pow2 - result)*(-1);

    printf("the result is %d\n", result);

    return 0;
}

4-4.c

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

#define DIGIT_NUM 40

void swap(char *a, char *b){
    char c = *a;
    *a = *b;
    *b = c;
}

void strrvs(char *str){
    int i, len = strlen(str);
    for(i=0;i<len/2;i++)swap(str+i, str+(len-i-1));
}

int main(){
    char result[DIGIT_NUM];
    int input, cnt = 0, seek = 0;
    unsigned int num;

    scanf("%d", &input);
    num = (unsigned int)input;

    do{
        result[seek++] = (num%2 ? '1':'0');
        num/=2;
        if(cnt++ % 4 == 3)result[seek++] = ' ';
    }while(num!=0);

    result[seek] = '\0';
    strrvs(result);
    printf("the result is %s\n", result);
    return 0;
}