题解 | #字符串解码#

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
        std::stack<int> multis;
        std::string res;
        std::string tmp;
        int multi = 0;
        for (int i = 0; i < s.size(); i++) {
            if (isdigit(s[i])) {
                multi = multi * 10 + s[i] - '0';
            } else if (s[i] == '[') {
                multis.push(multi);
                tmp.push_back(s[i]);
                multi = 0;
            }
            else if (s[i] == ']') {
                int idx = tmp.find_last_of("[");
                std::string core = tmp.substr(idx + 1);
                std::string prefix = tmp.substr(0, idx);
                int k = multis.top();
                multis.pop();
                std::string ss;
                for (int i = 0; i < k; i++) {
                    ss += core;
                }
                prefix += ss;
                tmp = prefix;
            } else {
                tmp.push_back(s[i]);
            }
        }

        return tmp;
    }
};