443. 压缩字符串 2021-08-21

class Solution {
private:
    inline int digital_length(int a) {
        int count = 0;
        while (a > 0) {
            ++count;
            a /= 10;
        }
        return count;
    }
    inline int put_num(vector<char> &chars, int start, int num) {
        int len = digital_length(num);
        for (int i = 1; i <= len; ++i) {
            chars[start + len - i] = '0' + (num % 10);
            num /= 10;
        }
        return len;
    }
public:
    int compress(vector<char> &chars) {
        char pre;
        int count;
        int ans = 0;
        pre = chars[0];
        count = 1;
        int i, j;
        for (i = 1, j = 0; i < chars.size(); ++i) {
            if (chars[i] == pre)
                ++count;
            else {
                chars[j++] = pre;
                ans += 1;
                if (count > 1) {
                    int len = put_num(chars, j, count);
                    j += len;
                    ans += len;
                }
                count = 1;
                pre = chars[i];
            }
        }
        chars[j++] = pre;
        ans += 1;
        if (count > 1) {
            int len = put_num(chars, j, count);
            ans += len;
        }
        return ans;
    }
};