Hello, coding enthusiasts! Today, we’re solving the “Longest Common Prefix” problem from LeetCode using Python and JavaScript.

## Problem Statement

Write a function to find the longest common prefix string amongst an array of strings.

If there is no common prefix, return an empty string `""`

.

**Example 1:**

```
Input: strs = ["flower","flow","flight"]
Output: "fl"
```

**Example 2:**

```
Input: strs = ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.
```

## Constraints

`1 <= strs.length <= 200`

`0 <= strs[i].length <= 200`

`strs[i]`

consists of only lowercase English letters.

## Analysis

The problem is straightforward. We need to find the longest common prefix among all the strings. The prefix is a sequence of characters at the beginning of each string.

## Approach

Here’s a step-by-step approach to solve this problem:

**Initialize Prefix:**We start with the prefix as the first string in the array.**Iterate Over Strings:**We iterate over each string in the array, starting from the second string.**Check Prefix:**We check if the current string starts with the prefix. If it doesn’t, we remove the last character from the prefix.**Update Prefix:**We continue removing the last character from the prefix until the current string starts with the prefix. If the prefix becomes an empty string, we return it.**Return Prefix:**After iterating over all the strings, the prefix will be the longest common prefix. We return this prefix as the result.

## Time Complexity

The time complexity of this approach is `O(n*m)`

, where n is the number of strings and m is the length of the largest string. This is because in the worst case, we are comparing m characters n times.

## Space Complexity

The space complexity is `O(1)`

, because we are not using any additional space that scales with the input size.

## Code

### Python

```
class Solution:
def longestCommonPrefix(self, strs: List[str]) -> str:
if not strs:
return ''
shortest_str = min(strs, key=len)
for i, char in enumerate(shortest_str):
for other in strs:
if other[i] != char:
return shortest_str[:i]
return shortest_str
```

### JavaScript

```
var longestCommonPrefix = function(strs) {
if (!strs.length) return '';
let prefix = strs[0];
for (let i = 1; i < strs.length; i++) {
while (strs[i].indexOf(prefix) !== 0) {
prefix = prefix.substring(0, prefix.length - 1);
if (!prefix.length) return '';
}
}
return prefix;
};
```

## Conclusion

In conclusion, the “Longest Common Prefix” problem is a great example of how we can apply simple string manipulation techniques to solve problems in computer science.

The solution has a time complexity of `O(n*m)`

and a space complexity of `O(1)`

, making it highly efficient.

Happy coding!

**Learn More:**

- LeetCode #13 – Roman to Integer
- LeetCode #12 – Integer to Roman
- LeetCode #11 – Container With Most Water
- LeetCode #10 – Regular Expression Matching
- LeetCode #8 – String to Integer (atoi)
- LeetCode #7 – Reverse Integer
- LeetCode #6 – Zigzag Conversion
- LeetCode #5 – Longest Palindromic Substring
- LeetCode #4 – Median of Two Sorted Arrays
- LeetCode #9 – Palindrome Number
- LeetCode – Longest Substring Without Repeating Characters
- LeetCode #2 – Add Two Numbers