Find the Index of the First Occurrence in a String
Problem Statement - link #
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.
Examples #
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 <= 10^4haystackandneedleconsist of only lowercase English characters.
Solutions #
class Solution {
public:
int strStr(string haystack, string needle) {
int res=-1;
int ns=needle.size(),hs=haystack.size();
if(ns>hs) return res;
for(int i=0;i<=hs-ns;i++){
if(haystack[i]==needle[0]){
int j=1;
for(;j<ns;j++){
if(haystack[i+j]!=needle[j]){
break;
}
}
if(j==ns){
res = i;
return res;
}
}
}
return res;
}
};