itoa的实现

#include <stdio.h>

char * itoa(int num, char *str, int len);
int main(void)
{
	int num = 12345;
	char str[7];
	int len = 5;
	char *pstr = itoa(num, str, len); 
	printf("The num string is:%s\n", pstr);
	printf("The num string is:%s\n", str);
	return 0;
}

char * itoa(int num, char *str, int len)
{
	if(len <= 0){
		printf("Len must bigger than 0\n");
		return NULL;
	}
	int i=0, j=0;
	char temp[len+1];
	while(num){// got reserved string
		temp[i] = num % 10 + '0';
		++i;
		num = num / 10;
	}
	temp[i] = 0; 
	printf("The temp string is:%s\n", temp);
	// reserved string again will got the right turn
	i = i - 1;
	while(i >= 0){
		str[j] = temp[i];
		++j;
		--i;
	}	
	str[j] = 0;
	return str;
}