LeetCode 28: Find the Index of the First Occurrence in a String
LeetCode 28 Solution Explanation
Explanation:
To find the index of the first occurrence of the needle string in the haystack string, we can iterate through the haystack string character by character. At each position, we check if the substring starting from that position matches the needle string. If a match is found, we return the current index as the result. If no match is found, we continue to the next character in the haystack string. If we reach the end of the haystack string without finding a match, we return -1.
-
Algorithm:
- Iterate through the
haystackstring character by character. - Check if the substring starting from the current position matches the
needlestring. - If a match is found, return the current index.
- If no match is found, continue to the next character.
- If no match is found after iterating through the entire
haystackstring, return -1.
- Iterate through the
-
Time Complexity: O((m-n)*n) where m is the length of
haystackand n is the length ofneedle. -
Space Complexity: O(1)
:
LeetCode 28 Solutions in Java, C++, Python
class Solution {
public int strStr(String haystack, String needle) {
if (needle.isEmpty()) {
return 0;
}
for (int i = 0; i <= haystack.length() - needle.length(); i++) {
if (haystack.substring(i, i + needle.length()).equals(needle)) {
return i;
}
}
return -1;
}
}Interactive Code Editor for LeetCode 28
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