implement-strStr.js

/**
 * 
 * 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().

 

Constraints:

haystack and needle consist only of lowercase English characters.
 */

var strStr = function (haystack, needle) {
    if (!needle) return 0;
    if (haystack.length < needle.length) return -1;
    const loopLength = haystack.length - needle.length;
    for (let i = 0; i <= loopLength; i++) {
        const currentStr = haystack.slice(i, needle.length + i);
        if (currentStr === needle) return i;
    }

    return -1;

};
const haystack = 'hello';
const needle = 'll';


const result = strStr(haystack, needle);

console.log('result-->', result);