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package string;

/**

* Created by gouthamvidyapradhan on 24/06/2017. Implement strStr().

*

* <p>Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part

* of haystack.

*

* <p>Solution O(N ^ 2)

*/

public class ImplementStrStr {

public static void main(String[] args) throws Exception {

System.out.println(new ImplementStrStr().strStr("AABB", ""));

}

public int strStr(String haystack, String needle) {

if (haystack.isEmpty() && needle.isEmpty()) return 0;

if (needle.isEmpty()) return 0;

for (int i = 0, l = haystack.length(); i < l; i++) {

if (haystack.charAt(i) == needle.charAt(0)) {

if (isEqual(haystack, needle, i)) return i;

}

}

return -1;

}

private boolean isEqual(String haystack, String needle, int i) {

int hL = haystack.length();

int nL = needle.length();

int j = 0;

while (i < hL && j < nL) {

if (haystack.charAt(i) != needle.charAt(j)) return false;

i++;

j++;

}

return j >= nL;

}

}