10进制转换为2~16进制

10进制数n转换为 base（2~16）进制的转换法则：除以base倒取余。
简单原理：n=(n/base) * base + n%base (此处的除法为整除)

如何倒着取余？使用栈的先进后出特性的来完成。

/*
 * @Author: jinbo.ma
 * @Mail: [email protected]
 * @Date: 2021-04-30 16:07:07
 * @LastEditTime: 2021-04-30 17:36:55
 */

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

#define MAX 1024
#define MIN 0
#define BASE_STACK_SIZE 20

/**
 * is legal input 
 * 1 => true
 * 0 => false
 **/
short is_legal_input(int base, int n) {
    if ( 2 > base || base > 16 ) {
        return 0;
    }

    if ( MIN > n || n > MAX ) {
        return 0;
    }

    return 1;
}

char * exchange(int base, int n) {
    short base_stack[BASE_STACK_SIZE], top = 0, index = 0;
    char base_storage[16] = {'0','1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
    char *res = (char*)calloc(sizeof(char), BASE_STACK_SIZE);
    while (n) {
        base_stack[top++] = n % base;
        n /=  base;
        printf("stack[%d]=%d n=%d\n", top-1, base_stack[top-1], n);
    }
    
    while (top) {
        res[index++] = base_storage[base_stack[--top]];
    }

    return res;
}


int main() {
    int base = 0, n = 0;
    
    printf("\nInput exchange base and number:");
    scanf("%d %d", &base, &n);
    
    if ( 0 == is_legal_input(base, n) ) {
        printf("Input isn't legal.\n");
        return 1;
    }

    char * p = exchange(base, n);
    printf("base=%d n=%d exchange=%s\n", base, n, p);
    
    return 0;
}

运行结果

# 十进制转二进制
Input exchange base and number:2 10
stack[0]=0 n=5
stack[1]=1 n=2
stack[2]=0 n=1
stack[3]=1 n=0
base=2 n=10 exchange=1010

# 十进制转八进制
Input exchange base and number:8 159
stack[0]=7 n=19
stack[1]=3 n=2
stack[2]=2 n=0
base=8 n=159 exchange=237

# 十进制转16进制
Input exchange base and number:16 255
stack[0]=15 n=15
stack[1]=15 n=0
base=16 n=255 exchange=FF

Input exchange base and number:16 1024
stack[0]=0 n=64
stack[1]=0 n=4
stack[2]=4 n=0
base=16 n=1024 exchange=400

# 十进制转换为七进制
Input exchange base and number:7 8
stack[0]=1 n=1
stack[1]=1 n=0
base=7 n=8 exchange=11

# 错误输入
Input exchange base and number:17 10
Input isn't legal.