LeetCode Tutorial in Python 28. Find the Index of the First Occurrence in a String
LeetCode Tutorial in Python 28. Find the Index of the First Occurrence in a String #python #leetcode
Solution 1 - Brute Force Approach:
Intuition:
The brute-force solution relies on a straightforward and intuitive approach. We iteratively check each position in the 'haystack' string to see if it matches the 'needle' string. If we find a match, we return the starting index of the match. If we reach the end of the loop without finding any matches, we return -1 to indicate that 'needle' is not present in 'haystack.'
Step-by-Step Breakdown:
We loop through the 'haystack' string character by character, starting from the first character.
At each iteration, we use slicing to extract a substring from 'haystack' of the same length as 'needle.'
We compare this substring with 'needle' to see if they match.
If they do match, we return the index where this match starts.
If we complete the loop without finding a match, we return -1.
Solution 2 - Python Built-in Method:
Intuition:
The second solution takes advantage of a built-in Python method, 'find,' which provides an efficient way to search for 'needle' within 'haystack.' This method returns the index of the first occurrence of 'needle' in 'haystack' or -1 if 'needle' is not found. The intuition here is to leverage Python's existing functionality to simplify the problem-solving process.
Step-by-Step Breakdown:
We use the 'find' method directly on the 'haystack' string.
The 'find' method searches for 'needle' within 'haystack.'
If 'needle' is found, it returns the index where the first occurrence starts.
If 'needle' is not found, it returns -1.
Analysis of Time & Space Complexities:
Solution 1:
Time Complexity: O(N) - The loop iterates through 'haystack' once, where N is the length of 'haystack.'
Space Complexity: O(1) - Minimal extra space is used, as we only store the loop variable 'i.'
Solution 2:
Time Complexity: O(N) - The 'find' method operates in O(N) time, where N is the length of 'haystack.'
Space Complexity: O(1) - Similar to Solution 1, it uses minimal additional memory.
Closing Thoughts:
Both solutions are valid approaches to solving this problem, but Solution 2 stands out for its simplicity and readability. However, understanding Solution 1's brute-force approach is essential, as it provides valuable insights into string manipulation and searching algorithms. Depending on the context and constraints of a real-world problem, you might choose one solution over the other.