B1078 字符串压缩与解压

题目：https://pintia.cn/problem-sets/994805260223102976/problems/994805262018265088

压缩的时候用了个trick，在最后一位加入了一个不可能字符

代码

#include<string>
#include<iostream>
using namespace std;
int main(){
    string str;
    char c;
    scanf("%c", &c);
    getchar();
    getline(cin, str);
    if(c == 'C'){
        str += str[str.size() - 1] + 1;
        int i = 0, j = 0;
        while( i != str.size() - 1){
            if(str[j] == str[i] && j < str.size() - 1){
                j++;
            } else {
                if(j - i == 1) printf("%c", str[i]);
                else printf("%d%c", j - i, str[i]);
                i = j;
            }
        }
    } 
    else if(c == 'D'){
        int i = 0;
        while(i < str.size()){
            if(str[i] <= '9' && str[i] >= '0'){
                int count = 0;
                while(str[i] <= '9' && str[i] >= '0'){
                    count *= 10;
                    count += str[i] - '0';
                    i++;
                }
                for(int j = 0; j < count; j++){
                    printf("%c", str[i]);
                }
                i++;
            } else {
                printf("%c", str[i]);
                i++;
            }
        }
    }
    return 0;
}