• Time:O(n)
• Space:O(1)

## C++

``````class Solution {
public:
int compress(vector<char>& chars) {
int ans = 0;

for (int i = 0; i < chars.size();) {
const char letter = chars[i];
int count = 0;
while (i < chars.size() && chars[i] == letter) {
++count;
++i;
}
chars[ans++] = letter;
if (count > 1)
for (const char c : to_string(count))
chars[ans++] = c;
}

return ans;
}
};
``````

## JAVA

``````class Solution {
public int compress(char[] chars) {
int ans = 0;

for (int i = 0; i < chars.length;) {
final char letter = chars[i];
int count = 0;
while (i < chars.length && chars[i] == letter) {
++count;
++i;
}
chars[ans++] = letter;
if (count > 1)
for (final char c : String.valueOf(count).toCharArray())
chars[ans++] = c;
}

return ans;
}
}
``````

## Python

``````class Solution:
def compress(self, chars: List[str]) -> int:
ans = 0
i = 0

while i < len(chars):
letter = chars[i]
count = 0
while i < len(chars) and chars[i] == letter:
count += 1
i += 1
chars[ans] = letter
ans += 1
if count > 1:
for c in str(count):
chars[ans] = c
ans += 1

return ans
``````