面试经典150题——Day23
文章目录
- 一、题目
- 二、题解
一、题目
28. Find the Index of the First Occurrence in a String
Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
Example 1:
Input: haystack = “sadbutsad”, needle = “sad”
Output: 0
Explanation: “sad” occurs at index 0 and 6.
The first occurrence is at index 0, so we return 0.
Example 2:
Input: haystack = “leetcode”, needle = “leeto”
Output: -1
Explanation: “leeto” did not occur in “leetcode”, so we return -1.
Constraints:
1 <= haystack.length, needle.length <= 104
haystack and needle consist of only lowercase English characters.
题目来源： leetcode
二、题解
class Solution {
public:
int strStr(string haystack, string needle) {
int n1 = haystack.length();
int n2 = needle.length();
int i = 0;
int res = n1;
while(i < n1){
int index = i;
int j = 0;
bool flag = true;
for(;j < n2;j++){
if(haystack[i++] != needle[j]){
flag = false;
break;
}
}
i = index + 1;
if(flag) res = min(index,res);
}
if(res == n1) return -1;
else return res;
}
};