char d =(char)intValue;

对于十六进制字符串中的每个2chars来执行此操作

如果字符串字符只有0-9A-F,则这样做：

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

int hex_to_int(char c){
        int first = c / 16 - 3;
        int second = c % 16;
        int result = first*10 + second;
        if(result > 9) result--;
        return result;
}

int hex_to_ascii(char c,char d){
        int high = hex_to_int(c) * 16;
        int low = hex_to_int(d);
        return high+low;
}

int main(){
        const char* st = "48656C6C6F3B";
        int length = strlen(st);
        int i;
        char buf = 0;
        for(i = 0; i < length; i++){
                if(i % 2 != 0){
                        printf("%c",hex_to_ascii(buf,st[i]));
                }else{
                        buf = st[i];
                }
        }
}