description:
mplement strStr().
Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
Note:
Example:
Example 1:
Input: haystack = "hello", needle = "ll"
Output: 2
Example 2:
Input: haystack = "aaaaa", needle = "bba"
Output: -1
my answer:
my answer:
class Solution {
public:
int strStr(string haystack, string needle) {
if(needle.size() == 0) return 0;
if(haystack.size() < needle.size()) return -1;//这里所有的特殊情况都要考虑周全,刚开始就没想到
for(int i = 0; i <= haystack.size() - needle.size() ; i++){
//这里注意i的循环范围,其中有一个测试是两个字符串都是一大长串的aaaaaaa长到一个一个比就oom了,但是其实他们相差的不是很多
for(int j = 0; j < needle.size(); j++){
if(needle[j] == haystack[i+j] && j == needle.size() - 1){
return i;
}
if(needle[j]!= haystack[i+j])break;
}
}
return -1;
}
};