# Longest Common Prefix

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 "".

```
class Solution {
public String longestCommonPrefix(String[] v) {
StringBuilder ans = new StringBuilder();
Arrays.sort(v);
String first = v[0];
String last = v[v.length-1];
for (int i=0; i<Math.min(first.length(), last.length()); i++) {
if (first.charAt(i) != last.charAt(i)) {
return ans.toString();
}
ans.append(first.charAt(i));
}
return ans.toString();
}
}
```

## Related Problems

Given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive.

There is only **one repeated number** in nums, return *this repeated number*.

You must solve the problem **without** modifying the array nums and uses only constant extra space.

Given an object, return a valid JSON string of that object. You may assume the object only inludes strings, integers, arrays, objects, booleans, and null. The returned string should not include extra spaces. The order of keys should be the same as the order returned by Object.keys().

Please solve it without using the built-in JSON.stringify method.

The Hamming Distance between two integers is the number of positions at which the corresponding bits are different.

Given two integers x and y, return *the ***Hamming distance*** between them*.

Given an unsorted array of integers nums, return *the length of the longest consecutive elements sequence.*

You must write an algorithm that runs in O(n) time.