AlgoDaily - Detect Substring in String

Detect Substring in String (Medium)

Good afternoon! Here's our prompt for today.

You may see this problem at Cisco, Autodesk, Salesforce, Zillow, Dropbox, Yelp, Databricks, Mailchimp, Samsara, Pipedrive, Grammarly, Digitalocean, Opendoor, and Docusign.

How would you write a function to detect a substring in a string?

If the substring can be found in the string, return the index at which it starts. Otherwise, return -1.

JAVASCRIPT

1function detectSubstring(str, subStr) {
2  return -1;
3}

Important-- do not use the native String class's built-in substring or substr method. This exercise is to understand the underlying implementation of that method.

Constraints

Length of both the given strings <=100000
The strings would never be null
The strings will only consist of lowercase letters
Expected time complexity : O(n)
Expected space complexity : O(1)

xxxxxxxxxx
​
 
var assert = require('assert');
​
console.log('Running and logging statements.');
​
function detectSubstring(str, subStr) {
  // Fill in this method
  return str;
}
​
console.log(detectSubstring('ggraph', 'graph'));
console.log(detectSubstring('geography', 'graph'));
console.log(detectSubstring('digginn', 'inn'));
​
try {
  assert.equal(detectSubstring('thepigflewwow', 'flew'), 6);
​
  console.log(
    'PASSED: ' + "`detectSubstring('thepigflewwow', 'flew')` should return `6`"
  );
} catch (err) {
  console.log(err);
}
​
try {
  assert.equal(detectSubstring('twocanplay', 'two'), 0);
​
  console.log(

OUTPUT

Results will appear here.