Str Str

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().

Solution:

var strStr = function (haystack, needle) {
  let result = 0;
  if (needle === "") {
    return result;
  }
  let index = haystack.indexOf(needle);
  return index >= -1 ? index : result;
};
console.log(strStr('hello', 'll'));
console.log(strStr('aaaaa', 'bba'));

Built-in:

function strStr2(haystack, needle) {
  return haystack.indexOf(needle);
}
console.log(strStr2('hello', 'll'));
console.log(strStr2('aaaaa', 'bba'));

Brute force:

function strStr3(haystack, needle) {
  for (let i = 0; i < haystack.length - needle.length + 1; i++) {
    if (haystack.substr(i, needle.length) === needle) return i;
  }
  return -1;
}
console.log(strStr3('hello', 'll'));
console.log(strStr3('aaaaa', 'bba'));