28. Implement strStr()
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().
Solution
class Solution {
public int strStr(String haystack, String needle) {
for(int i = 0;; i++) {
for(int j = 0;; j++){
//if it goes to the end of needle without problems
if(j == needle.length()) return i;
//check if we are end of haystack
if(i+j == haystack.length()) return -1;
//check if the char is equal
if(haystack.charAt(i+j) != needle.charAt(j)) break;
}
}
}
}
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