难度:Easy
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: 2Example 2:Input: haystack = "aaaaa", needle = "bba"Output: -1Clarification: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().
主要是判断特殊情况,其他直接比较就行。
class Solution {public:int strStr(string haystack, string needle) {int n_len=needle.length();int h_len=haystack.length();if(n_len==0) return 0;if(n_len>h_len) return -1;if(n_len == h_len) return haystack == needle? 0:-1;for(int i=0;i<h_len-n_len+1;i++)if(haystack[i] == needle[0] && haystack.substr(i,n_len) == needle) return i;return -1;}};
执行用时 :4 ms, 在所有 C++ 提交中击败了93.87%的用户 内存消耗 :9 MB, 在所有 C++ 提交中击败了84.51%的用户