Daily practice of C language - day 3: calculate the number of occurrences of sub strings of strings

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

#define MAX_LENGTH 256

int get_sum_child_string(char *str, char *child_str);

int main()
{
    
	char string[MAX_LENGTH];
	char child_string[MAX_LENGTH];
	printf(" Please enter string and substring respectively - The string does not contain spaces \n");
	scanf("%s%s", string, child_string);
	printf(" Substring occurrences are  %d\n",\
	       get_sum_child_string(string, child_string));
	return 0;
	
 } 
 /** *@brief  from str Search for child_str *@return  Number of matched substrings  */
 int get_sum_child_string(char *str, char *child_str)
 {
    
 	int sum = 0;
 	int i = 0;
 	int str_len = strlen(str);
 	int child_str_len = strlen(child_str);
    
	
	/* Judge whether the data is reasonable  */
	if(str == NULL || child_str == NULL || str_len < child_str_len)
	{
    
		return 0;
		}	
 	while(strlen(str) >= child_str_len)
 	{
    
 		/* Word string matching  */
		 for(i = 0; i < child_str_len; i++)
		 {
    
		 	if(str[i] != child_str[i])
		 	   break;
		  } 
		  /* Match to string  */
		  if(i == child_str_len)
		  {
    
		  	sum++;
		  	str += child_str_len;
		   } 
		   else str++;
	 }
	 
	 return sum;
 }