CareerCup

#include "stdafx.h"
#include <iostream>
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
	char str1[] = "HelloWorld123";
	char str2[] = "World";

	int n1 = strlen(str1);
	int n2 = strlen(str2);

	char *s1,s2;
	s1 = str1;
	for(int i=0; s1[i]; i++)
	{
		char *s3=s1+i;
		char *s4 = str2;
		for(;(*s4 == *s3) && (s3!='\0' && s4!= '\0');s3++,s4++ )
		{
		}
		if(*s4 == '\0')
		{
			cout << (i+n2-1) << endl;
			break;
		}
	}

	return 0;
}

Use autometa. N =Input String Length, Time O(N), Space O(1)

/*Assuming that input pointers are valid*/
int patternMatch (char* pInputStr, char* pPattern)
{
int inputLen = strlen (pInputStr);
int patternLen = strlen (pPattern);
int indexInPattern = patternLen - 1;
int indexInInput = inputLen - 1;
int returnIndex = -1;

while (indexInPattern >= 0)
{
if (pInputStr [indexInInput] == pPattern [indexInPattern])
{
indexInPattern --;
}
else
{
indexInPattern = patternLen - 1;
}
if (indexInPattern == -1)
{
returnIndex = indexInInput;
break;
}
indexInInput --;
}
return returnIndex;
}

Use autometa. N =Input String Length, Time O(N), Space O(1)

/*Assuming that input pointers are valid*/
int patternMatch (char* pInputStr, char* pPattern)
{
int inputLen = strlen (pInputStr);
int patternLen = strlen (pPattern);
int indexInPattern = patternLen - 1;
int indexInInput = inputLen - 1;
int returnIndex = -1;

while (indexInPattern >= 0)
{
if (pInputStr [indexInInput] == pPattern [indexInPattern])
{
indexInPattern --;
}
else
{
indexInPattern = patternLen - 1;
}
if (indexInPattern == -1)
{
returnIndex = indexInInput;
break;
}
indexInInput --;
}
return returnIndex;
}

int Findsubstring(Char* s1,char* s2)
{
int l=strlen(s1);int m=strlen(s2);
if(m>n)
{
for(int i=0;i<=m-n;i++)
if(strcmp(substr(s1,i,i+n),s2)==0)
return i+n;
}
else
{
for(int i=0;i<=n-m;i++)
if(strcmp(substr(s2,i,i+m),s1)==0)
return i+m;
}
}

use KMP or Rabin Carp !

Why not just use find() and add the length of the string to the position.