Implement strStr().
Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
Example 1:
Input: haystack = “hello”, needle = “ll”
Output: 2
Example 2:
Input: haystack = “aaaaa”, needle = “bba”
Output: -1
Clarification:
What should we return when needle is an empty string? This is a great question to ask during an interview.
For the purpose of this problem, we will return 0 when needle is an empty string. This is consistent to C’s strstr() and Java’s indexOf().
public static int strStr1(String haystack, String needle){for(int i=0; ;i++){for(int j = 0; ;j++){if(j == needle.length()) return i;if(j+i == haystack.length()) return -1;if(needle.charAt(j) != haystack.charAt(i+j)) break;}}}public static int strStr(String haystack, String needle){int l1 = haystack.length();int l2 = needle.length();if(l1 < l2)return -1;else if(l2 ==0)return 0;int threshold = l1 - l2;for(int i = 0; i < threshold;i++){if(haystack.substring(i,i+l2).equals(needle))return i;}return -1;}