HUAWEI OD machine test real test JavaScript implementation [Find the longest common substring in two strings a, b] [Niu Ke practice questions]

1. Topic description

Find the longest common substring of two strings a, b. If there are more than one, output the one that appears first in the shorter string.

Note: Definition of substring: A string formed by deleting the prefix and suffix (or not) from a string. Please separate from the concept of "subsequence"!

Data range: string length 1≤length≤300.

2. Enter description

Enter two strings.

3. Output description

Returns repeated occurrences of characters.

4. Problem-solving ideas

1. First read the two input strings;
2. Determine which string is shorter, use it as a short string, and the other string as a long string;
3. Get the length of short string and long string;
4. Initialize the variables maxLen and start, which are used to record the length and starting position of the longest common substring respectively;
5. Use two layers of loops, the outer loop traverses the short string, and the inner loop traverses the substrings in the short string;
6. In each inner loop, judge whether the current substring is a substring of a long string, and compare whether its length is greater than the maximum length of the previous record;
7. If the conditions are met, update the maximum length maxLen and the starting position start;
8. After the loop ends, the longest common substring is extracted from the short string according to the maximum length and the starting position, and output.

5. JavaScript algorithm source code