練習3.5

編寫函數itob(n,s,b)，將整數n轉換成以b爲底的數，並將轉換結果以字符串形式保存在字符串中。

 

代碼：

 

 

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

void itob(int n, char s[], short b);
void reverse(char *s);
int main(int argc, char *argv[])
{
    int n = INT_MIN;
    char s[30] = "";
    itoa(n, s, 10);
    printf("%s\n", s);

    char s1[30] = "";
    itob(n, s1, 16);
    printf("%s\n", s1);
    itob(n, s1, 8);
    printf("%s\n", s1);

    itob(n, s1, 2);
    printf("%s\n", s1);
    return 0;
}
void reverse(char *s)
{
    int i = 0;
    int j = strlen(s)-1;
    while (i < j) {
        char item = s[i];
        s[i] = s[j];
        s[j] = item;
        ++i,--j;
    }
}
void itob(int n, char s[], short b)
{
    char neg = 'n';
    if (n < 0)
        neg = 'y';
    if (neg == 0) {
        s[0] = '0';
        s[1] = '\0';
        return ;
    }
    int i = 0;
    while (n != 0) {
        int k = n % b;
        if (k < 0)
            k = -k;

        if (k >= 0 && k <= 9)
            s[i++] = '0'+k;
        else if (k >= 10 && k<= 15)
            s[i++] = 'a' + k - 10;
        else
            s[i++] = '#';
        n /= b;
    }
    if (neg == 'y')
        s[i++] = '-';
    s[i] = '\0';
    reverse(s);
}