# 443.String Compression

Given an array of characters, compress it in-place.

The length after compression must always be smaller than or equal to the original array.

Every element of the array should be a character (not int) of length 1.

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

Follow up: Could you solve it using only O(1) extra space?

`Example 1:​Input:["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:"aa" is replaced by "a2". "bb" is replaced by "b2". "ccc" is replaced by "c3".​​Example 2:​Input:["a"]​Output:Return 1, and the first 1 characters of the input array should be: ["a"]​Explanation:Nothing is replaced.​​Example 3:​Input:["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:Since the character "a" does not repeat, it is not compressed. "bbbbbbbbbbbb" is replaced by "b12".Notice each digit has it's own entry in the array.​​Note:​All characters have an ASCII value in [35, 126].1 <= len(chars) <= 1000.`

`class Solution {public:    int compress(vector<char>& chars) {        int start=1;        int count=1;        int res=0;        for(int i=1;i<chars.size();i++)        {            if(chars[i]==chars[i-1])                count++;            else            {                if(count==1){                    res+=1;                }                else                {                    string tmp=to_string(count);                    res+=1+tmp.length();                    for(auto c:tmp)                        chars[start++]=c;                             count=1;​                 }                chars[start++]=chars[i];            }                          }​         if(count==1){                    res+=1;                }                else                {                    string tmp=to_string(count);                    res+=1+tmp.length();                    for(auto c:tmp)                        chars[start++]=c;                          }            return res;    }};`