## Algorithm

Problem Name: 443. String Compression

Given an array of characters `chars`, compress it using the following algorithm:

Begin with an empty string `s`. For each group of consecutive repeating characters in `chars`:

• If the group's length is `1`, append the character to `s`.
• Otherwise, append the character followed by the group's length.

The compressed string `s` should not be returned separately, but instead, be stored in the input character array `chars`. Note that group lengths that are `10` or longer will be split into multiple characters in `chars`.

After you are done modifying the input array, return the new length of the array.

You must write an algorithm that uses only constant extra space.

Example 1:

```Input: chars = ["a","a","b","b","c","c","c"]
Output: Return 6, and the first 6 characters of the input array should be: ["a","2","b","2","c","3"]
Explanation: The groups are "aa", "bb", and "ccc". This compresses to "a2b2c3".
```

Example 2:

```Input: chars = ["a"]
Output: Return 1, and the first character of the input array should be: ["a"]
Explanation: The only group is "a", which remains uncompressed since it's a single character.
```

Example 3:

```Input: chars = ["a","b","b","b","b","b","b","b","b","b","b","b","b"]
Output: Return 4, and the first 4 characters of the input array should be: ["a","b","1","2"].
Explanation: The groups are "a" and "bbbbbbbbbbbb". This compresses to "ab12".```

Constraints:

• `1 <= chars.length <= 2000`
• `chars[i]` is a lowercase English letter, uppercase English letter, digit, or symbol.

## Code Examples

### #1 Code Example with Java Programming

```Code - Java Programming```

``````
class Solution {
public int compress(char[] chars) {
int idx = 0;
int startIdx = 0;
while (idx < chars.length) {
char c = chars[idx];
int count = 0;
while (idx < chars.length && chars[idx] == c) {
idx++;
count++;
}
chars[startIdx++] = c;
if (count > 1) {
String countString = String.valueOf(count);
for (char cs : countString.toCharArray()) {
chars[startIdx++] = cs;
}
}
}
return startIdx;
}
}
``````
Copy The Code &

Input

cmd
chars = ["a","a","b","b","c","c","c"]

Output

cmd
Return 6, and the first 6 characters of the input array should be: ["a","2","b","2","c","3"]

### #2 Code Example with Javascript Programming

```Code - Javascript Programming```

``````
const compress = function(chars) {
let indexAns = 0
let index = 0
while(index < chars.length) {
let currentChar = chars[index]
let count = 0
while(index < chars.length && chars[index] === currentChar) {
index++
count++
}
chars[indexAns++] = currentChar
if(count !== 1) {
for(let el of (''+count).split('')) {
chars[indexAns++] = el
}
}
}
return indexAns
};
``````
Copy The Code &

Input

cmd
chars = ["a","a","b","b","c","c","c"]

Output

cmd
Return 6, and the first 6 characters of the input array should be: ["a","2","b","2","c","3"]

### #3 Code Example with Python Programming

```Code - Python Programming```

``````
class Solution:
def compress(self, chars):
"""
:type chars: List[str]
:rtype: int
"""
curr, count, i = chars, 1, 1
while i1: chars[:i]+= (i for i in "".join(str(count))); i+=len([i for i in "".join(str(count))])
i, count =i+1, 1
else:
if i==len(chars)-1: chars.pop(i); chars+=[i for i in "".join(str(count+1))]; break
chars.pop(i); count+=1
return len(chars)
``````
Copy The Code &

Input

cmd
chars = ["a"]

Output

cmd
Return 1, and the first character of the input array should be: ["a"]

### #4 Code Example with C# Programming

```Code - C# Programming```

``````
namespace LeetCode
{
public class _0443_StringCompression
{
public int Compress(char[] chars)
{
int index = 0, count = 0;
char current = chars;
for (int i = 0; i < chars.Length; i++)
{
if (chars[i] == current)
count++;
else
{
chars[index++] = current;

if (count > 1)
{
var countStr = count.ToString();
foreach (var ch in countStr)
chars[index++] = ch;
}

current = chars[i];
count = 1;
}
}

chars[index++] = current;
if (count > 1)
{
var countStr = count.ToString();
foreach (var ch in countStr)
chars[index++] = ch;
}

return index;
}
}
}
``````
Copy The Code &

Input

cmd
chars = ["a"]

Output

cmd
Return 1, and the first character of the input array should be: ["a"]