题目描述:
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().
题源:here;完整代码:here
思路:
遍历haystack,如果有与needle相同的情况就看haystack和needle之后的是否相同。
代码
int strStr(string haystack, string needle) {
if (needle.size() == 0) return 0;
if (haystack.size() == 0) return -1;
for (int i = 0; i < haystack.size(); i++){
int needle_idx = 0;
int haystack_idx = i;
while (haystack_idx < haystack.size() &&\
needle_idx < needle.size() &&\
haystack[haystack_idx] == needle[needle_idx])
{
needle_idx++;
haystack_idx++;
}
if (needle_idx == needle.size()) return i;
}
return -1;
}