LeetCode-in-Java
28. Find the Index of the First Occurrence in a String
Easy
Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
Example 1:
Input: haystack = “sadbutsad”, needle = “sad”
Output: 0
Explanation: “sad” occurs at index 0 and 6. The first occurrence is at index 0, so we return 0.
Example 2:
Input: haystack = “leetcode”, needle = “leeto”
Output: -1
Explanation: “leeto” did not occur in “leetcode”, so we return -1.
Constraints:
1 <= haystack.length, needle.length <= 104haystackandneedleconsist of only lowercase English characters.
Solution
public class Solution {
public int strStr(String haystack, String needle) {
if (needle.isEmpty()) {
return 0;
}
int m = haystack.length();
int n = needle.length();
for (int start = 0; start < m - n + 1; start++) {
if (haystack.substring(start, start + n).equals(needle)) {
return start;
}
}
return -1;
}
}