題目:
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().
題意:
判斷第二個字元串是否是第一個字元串的子串,若是,傳回第二個字元串第一個字元在第一個字元串出現的下标;若不是,傳回-1;若第二個字元串為空字元串,傳回0。
思路:
一道easy的題,就不去弄什麼KMP、manacher算法了,簡單點,暴力過
Code:
class Solution {
public:
int strStr(string haystack, string needle) {
int m=haystack.size(),n=needle.size();
if(!n) return 0;
if (n>m) return -1;
for (int i=0;i<=m-n;i++){
int j=0;
for (;j<n;j++){
if (haystack[i + j]!=needle[j]) break;
}
if (j==n) return i;
}
return -1;
}
};