Problem
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
/**
* @param {string} haystack
* @param {string} needle
* @return {number}
*/
var strStr = function(haystack, needle) {
var len1 = haystack.length;
var len2 = needle.length;
if (!len2) return 0;
for (var i = 0; i < len1; i++) {
for (var j = 0; j < len2; j++) {
if (i + j === len1) return -1;
if (haystack[i + j] !== needle[j]) break;
if (j === len2 - 1) return i;
}
}
return -1;
};
Explain:
nope.
Complexity:
- Time complexity : O(n*m).
- Space complexity : O(1).