Problem Statement
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.
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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.
- Time: O((m – n)n)O((m−n)n), where m = |\texttt{haystack}|m=∣haystack∣ and n = |\texttt{needle}|n=∣needle∣
- Space: O(1)O(1)
Find The Index Of The First Occurrence In A String Program Solution in C++
class Solution {
public:
int strStr(string haystack, string needle) {
const int m = haystack.length();
const int n = needle.length();
for (int i = 0; i < m - n + 1; i++)
if (haystack.substr(i, n) == needle)
return i;
return -1;
}
};
Find The Index Of The First Occurrence In A String Program Solution in JAVA
class Solution {
public int strStr(String haystack, String needle) {
final int m = haystack.length();
final int n = needle.length();
for (int i = 0; i < m - n + 1; ++i)
if (haystack.substring(i, i + n).equals(needle))
return i;
return -1;
}
}
Find The Index Of The First Occurrence In A String Program Solution in Python
class Solution:
def strStr(self, haystack: str, needle: str) -> int:
m = len(haystack)
n = len(needle)
for i in range(m - n + 1):
if haystack[i:i + n] == needle:
return i
return -1
