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class Solution {
    public static void main(String[] args)
	{/*
		String s1 = "mississippi";
		String s2 = "pi";
		
		*/
		String s1 = "mississippi";
		String s2 = "issipi";
	System.out.println(strStr(s1, s2));
		}
    public static int strStr(String haystack, String needle) {

        char[] hayChar = haystack.toCharArray();
        char[] neeChar = needle.toCharArray();
        char head;
        if (needle == null || needle.length() == 0 || haystack.equals(needle))
            return 0;
        else if(haystack == null || haystack.length() == 0 || haystack.length() < needle.length())
            return -1;
      
        else 
            head = neeChar[0];
        int k = 0;
		int n = 0;
        //System.out.println("k="+k);

        for1:
        for(int i = 0; i < hayChar.length; i++)
		{
           
			if (hayChar[i] == head)
			{
				k = i;//k=8
				n = i;
				for2:
				for(int j = 0; j < neeChar.length; j++)
                {
                 
                    System.out.println("j="+j);
					System.out.println("k="+k);
					if(neeChar[j] != hayChar[k] )
                       continue for1;

					if(k == hayChar.length-1 && j == neeChar.length-1 )
							break for2;
					else if (k == hayChar.length-1 && j != neeChar.length-1 )
					{
						return -1;
					} 
					else
						k++;

                }
                System.out.println("n="+n);
               return n;
			}
			
		}

        
    return -1;
    }
}

public int strStr(String haystack, String needle) {
    int m = haystack.length(), n = needle.length();
    if (n == 0) return 0;
    for (int i = 0; i <= m - n; i++) {
        for (int j = 0; j < n; j++) {
            if (haystack.charAt(i + j) != needle.charAt(j)) break;
            if (j == n - 1) return i;
        }
    }
    return -1;
}

class Solution {
  public int strStr(String haystack, String needle) {
    int L = needle.length(), n = haystack.length();

    for (int start = 0; start < n - L + 1; ++start) {
      if (haystack.substring(start, start + L).equals(needle)) {
        return start;
      }
    }
    return -1;
  }
}