2023-12-09 18:42:21 +08:00
< p > Given two strings < code > needle< / code > and < code > haystack< / code > , return the index of the first occurrence of < code > needle< / code > in < code > haystack< / code > , or < code > -1< / code > if < code > needle< / code > is not part of < code > haystack< / code > .< / p >
< p > < / p >
< p > < strong class = "example" > Example 1:< / strong > < / p >
< pre >
< strong > Input:< / strong > haystack = " sadbutsad" , needle = " sad"
< strong > Output:< / strong > 0
< strong > Explanation:< / strong > " sad" occurs at index 0 and 6.
The first occurrence is at index 0, so we return 0.
< / pre >
< p > < strong class = "example" > Example 2:< / strong > < / p >
< pre >
< strong > Input:< / strong > haystack = " leetcode" , needle = " leeto"
< strong > Output:< / strong > -1
< strong > Explanation:< / strong > " leeto" did not occur in " leetcode" , so we return -1.
< / pre >
< p > < / p >
< p > < strong > Constraints:< / strong > < / p >
< ul >
< li > < code > 1 < = haystack.length, needle.length < = 10< sup > 4< / sup > < / code > < / li >
< li > < code > haystack< / code > and < code > needle< / code > consist of only lowercase English characters.< / li >
< / ul >
