题解 | #牛牛的字符串解码问题#

#include <cctype>
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param s string字符串 
     * @return string字符串
     */
    string decodeString(string s) 
    {
        // write code here
        string ans;
        int i = 0;
        
        while (i < s.length()) {
            if (isalpha(s[i])) {
                ans += s[i];
                i++;
            } else if (isdigit(s[i])) {
                int repeat = 0;
                while (isdigit(s[i])) {
                    repeat = repeat * 10 + (s[i] - '0');
                    i++;
                }
                i++; // skip '['
                
                int start = i;
                int count = 1;
                while (count > 0) {
                    i++;
                    if (s[i] == '[') count++;
                    else if (s[i] == ']') count--;
                }
                string repeatedStr = decodeString(s.substr(start, i - start));
                
                for (int j = 0; j < repeat; j++) {
                    ans += repeatedStr;
                }
                i++; // skip ']'
            }
        }
        
        return ans;
    }
};