C language program practice - (write a function, its prototype is int continumax (char *outputstr, char *intputstr))

Write a function , Its original form is int continumax(char *outputstr,char *intputstr).
function ：
Find the longest consecutive number string in the string , And return the length of this string ,
And give the longest string of numbers to one of the function parameters outputstr The memory in question .
for example ："abcd12345ed125ss123456789" Send the first address of to intputstr after , Function will return 9,
outputstr The value indicated is 123456789

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

int continumax(char *outputstr, char *intputstr)
{
    
	int max_num_len = 0;
	int flag = 0;
	int i = 0;
	int count = 0;
	int area_i = 0;
	int area_end_i = 0;
	char *tmp = intputstr;
	char s1[1024];
	while(tmp[i] != '\0')
	{
    
		if(tmp[i] > 47 && tmp[i] < 58)
		{
    
			if(flag == 0)
			{
    
				area_i = i;
				flag = 1;
				count++;
			}
			else if(flag == 1)
			{
    
				count++;
			}
			++i;
		}
		else
		{
    
			if(flag == 1)
			{
    
				if(count > max_num_len)
				{
    
					area_end_i = i;
					max_num_len = count;
					int j;
					for(j = area_i;j < area_end_i;j++)
					{
    
						outputstr[j - area_i] = intputstr[j];
						
					}
				}
				count = 0;
				flag = 0;
			}
			++i;
		}
		
	}
	if(flag == 1)
			{
    
				if(count > max_num_len)
				{
    
					area_end_i = i;
					max_num_len = count;
					int j;
					for(j = area_i;j < area_end_i;j++)
					{
    
						outputstr[j - area_i] = intputstr[j];
					}
					
				}
				count = 0;
				flag = 0;
			}
	return max_num_len;
}

int main ()
{
    
	char *str = "abd1234xsac2231231xasc111";
	char *outputstr = (char *)malloc(1024); 
	int intputstr = continumax(outputstr, str);
	printf("intputstr = %d\n", intputstr);
	printf("outputstr = %s\n", outputstr);
	return 0;
}
/* continumax(outputstr, str);  This , Just passed in the pointer  , use  continumax(char *outputstr, char *intputstr)  After that , Will degenerate into pointer variables , It can only be modified malloc The value of the inside , It can't be modified  outputstr Point to  continumax(&outputstr, str);  This incoming pointer address , use  continumax(char **outputstr, char *intputstr)  Connect it with the secondary pointer , Can modify output Point to  */