覆盖 C 中的字符串

Question

我正在尝试创建一个代码，将十进制转换为 2 到 16 之间的任何基数。但是我不知道如何在字符串中写入新值。

void base_conversion(char s[], int x, int b) {
int j, y;
j = 0;
// your code here
while(b > 1 && b < 17) {
    if (x < 0) {
        x = (-x);
    }else if(x == 0) {
        s[j] = '';
    }
        x = (x/b);
    while(x > 0) {
        y = (x%b);

        if (y == 10) {
            s[j] = 'A';
        }else if(y == 11) {
            s[j] = 'B';
        }else if(y == 12) {
            s[j] = 'C';
        }else if(y == 13) {
            s[j] = 'D';
        }else if(y == 14) {
            s[j] = 'E';
        }else if(y == 15) {
            s[j] = 'F';
        }else{
            s[j] = y;
        }
    }
}j = j + 1;
}

Answer 1

你快到了，虽然有几个错误，所以我"改进"了你的代码。无限循环测试基础，只需要完成一次。while()循环组织得不太正确 - x/b数字提取循环之外完成的。我所做的另一个更改是使用查找数组将每个数字转换为一个字符，这节省了大量费力的测试。我还返回了作为函数值传递的字符串 - 不妨添加更多功能。在传递错误的基值的情况下，我本可以返回NULL而不是空字符串。另请注意，我在将其用作索引的相同语句中更新了j，这使代码更加流畅。

#include <stdio.h>
char *base_conversion (char *s, int x, int b) {
    char charr[] = "0123456789ABCDEF";
    int i, j = 0, len, digit, neg = 0;
    *s = 0;                     // terminate the string passed
    if (b < 2 || b > 16)        // check the base
        return s;               // return an empty string
    if (x < 0) {
        x = -x;                 // adjust for negative input
        neg = 1;
    }
    do {
        digit = x % b;          // extract each l.s. digit
        s[j++] = charr [digit]; // convert to character
    } while (x /= b);           // implicitly test for 0
    if (neg)                    // negative input
        s[j++] = '-';           // append a minus sign
    s[j] = 0;                   // terminate the string
    // reverse the string
    len = j;
    for (i=0; i<len/2; i++) {
        digit = s[i];
        s[i] = s[--j];          // pre-decrement j to next char index
        s[j] = digit;
    }
    return s;
}    
int main () { 
    int n;
    char strig[65];
    for (n=1000; n>=-1000; n-=2000) {
        printf ("Binary      %d: %sn", n, base_conversion (strig, n, 2)); 
        printf ("Ternary     %d: %sn", n, base_conversion (strig, n, 3)); 
        printf ("Octal       %d: %sn", n, base_conversion (strig, n, 8)); 
        printf ("Decimal     %d: %sn", n, base_conversion (strig, n, 10)); 
        printf ("Hexadecimal %d: %sn", n, base_conversion (strig, n, 16)); 
    }
    return 0;
}

程序输出：

Binary      1000: 1111101000
Ternary     1000: 1101001
Octal       1000: 1750
Decimal     1000: 1000
Hexadecimal 1000: 3E8
Binary      -1000: -1111101000
Ternary     -1000: -1101001
Octal       -1000: -1750
Decimal     -1000: -1000
Hexadecimal -1000: -3E8