#include <stddef.h>


unsigned int mystrlen(char *s)
{
	if(s==NULL)
		return 0;

	unsigned int i;
	for(i=0;s[i]!=0;i++);
	return i;
}

char *mystrchr(char *s, char c)
{
	if(s==NULL)
		return NULL;
	int i;
	for(i=0;s[i]!=0;++i)
	{
		if(s[i]==c)
			return &s[i];
	}
	return NULL;
}


char *mystrcpy(char *dest, char *src)
{
	if(src==NULL && dest==NULL)
		return NULL;

	int i;
	for(i=0;src[i]!=0;++i)
	{
		dest[i]=src[i];
	}
	dest[i]=0;
	return dest;
}

char *mystrcat(char *dest, char *src)
{
	if(dest==NULL && src==NULL)
		return NULL;

	int x=mystrlen(dest);
	int i,j=0;

	for(i=x;src[j]!=0;++i)
	{
		dest[i]=src[j];
		j++;
	}
	return dest;
}

int mystrcmp(char *s1, char *s2)
{
	if(s1==NULL && s2==NULL)
		return 0;

	int i;
	for(i=0;s1[i]!=0 || s2[i]!=0;++i)
	{
	if(s1[i]>s2[i])
		return 1;
	if(s1[i]<s2[i])
		return -1;
	}
	return 0;
}