代码如下：

#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

int dectohex(int b, char array[])
{
	char a[17] = { "0123456789ABCDEF" };
	int c[30] = { 0 }, i = 0, base = 16, j = 0;
	while (b)
	{
		c[i++] = b % base;
		b = b / base;
	}
	j = i;
	for (i--; i >= 0; i--)
		array[i] = a[c[i]];
	return j;
}

int main()
{
	char arr[100];
	int b = 0, n = 0;
	printf("请输入一个十进制数\n");
	scanf("%d", &b);
	n = dectohex(b, arr);
	printf("%d的十六进制为:", b);
	for (n--; n >= 0; n--)
		printf("%c", arr[n]);
}

结果如下：