Description
Implement strStr().
Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
Input: haystack = "hello", needle = "ll"
Output: 2
Input: haystack = "aaaaa", needle = "bba"
Output: -1
Solution
- 穷举遍历
实现string的strStr()，借助于substr方法，能AC
int strStr(string haystack, string needle) {
int len1 = haystack.size(), len2 = needle.size();
if (len1 < len2) {
return -1;
}
for (int i = 0; i < len1 - len2 + 1; ++i) {
if (haystack.substr(i, len2) == needle) {
return i;
}
}
return -1;
}
- KMP算法
