Integer to hexadecimal string PTA

This problem requires the implementation of a long integer into 16 Simple function of hexadecimal string .

Function interface definition ：

void f( long int x, char *p );

among x Is the decimal long integer to be converted ,p Point to the first element of a character array . function f The function of is to convert the 16 Hexadecimal string write p The array pointed to .16 It's binary A~F For capital letters .

Sample referee test procedure ：

#include <stdio.h>
#define MAXN 10

void f( long int x, char *p );

int main()
{
    long int x;
    char s[MAXN] = "";
    
    scanf("%ld", &x);
    f(x, s);
    printf("%s\n", s);
    
    return 0;
}

/*  Your code will be embedded here  */

sample input 1：

123456789

sample output 1：

75BCD15

sample input 2：

-125

sample output 2：

-7D

void f( long int x, char *p ){
    if(x==0){
        *p='0';
    }
    if(x<0){
        x=-x;
        *p='-';
        p++;
    }
    long int a=x;int ctn=0;
    while(x!=0){
        x/=16;
        ctn++;
    }
    for(int i=0;i<ctn;i++){
        int t=a%16;
        if(t<10){
            *(p+ctn-1-i)=t+'0';
        }else{
            *(p+ctn-1-i)=t+'A'-10;
        }
        a/=16;
    }
}