字符串解码 图解题解

# 嵌套/括号题判据：遇到『开始符』要不要存现场？遇到『结束符』要不要弹栈合并？
num_stack, str_stack = [], []
cur, num = '', 0
for ch in s:
    if 是数字: num = num*10 + 值       # 累计本层参数
    elif 是开始符:                      # 进内层
        num_stack.append(num)           # 存现场
        str_stack.append(cur)
        cur, num = '', 0                # 重置
    elif 是结束符:                      # 出内层
        k = num_stack.pop()             # 弹现场
        cur = str_stack.pop() + cur*k   # 合并(前缀在前)
    else: cur += ch
return cur

vector<int> numStk; vector<string> strStk;
string cur; int num = 0;
for (char ch : s) {
    if (isdigit(ch)) num = num*10 + (ch-'0');   // 累计参数
    else if (是开始符) {                         // 存现场
        numStk.push_back(num); strStk.push_back(cur);
        cur = ""; num = 0;
    } else if (是结束符) {                       // 弹栈合并
        int k = numStk.back(); numStk.pop_back();
        string prev = strStk.back(); strStk.pop_back();
        string rep; while (k--) rep += cur; cur = prev + rep;
    } else cur += ch;
}
return cur;

Deque<Integer> numStk = new ArrayDeque<>();
Deque<String> strStk = new ArrayDeque<>();
StringBuilder cur = new StringBuilder(); int num = 0;
for (char ch : s.toCharArray()) {
    if (Character.isDigit(ch)) num = num*10 + (ch-'0'); // 累计参数
    else if (是开始符) {                                  // 存现场
        numStk.push(num); strStk.push(cur.toString());
        cur = new StringBuilder(); num = 0;
    } else if (是结束符) {                                // 弹栈合并
        int k = numStk.pop(); String prev = strStk.pop();
        StringBuilder sb = new StringBuilder(prev);
        while (k-- > 0) sb.append(cur); cur = sb;
    } else cur.append(ch);
}
return cur.toString();