题目
给定一个字符串 s 表示一个整数嵌套列表，实现一个解析它的语法分析器并返回解析的结果 NestedInteger 。
列表中的每个元素只可能是整数或整数嵌套列表
示例
示例 1：
输入：s = “324”, 输出：324 解释：你应该返回一个 NestedInteger 对象，其中只包含整数值 324。
示例 2：
输入：s = “[123,[456,[789]]]”, 输出：[123,[456,[789]]] 解释：返回一个 NestedInteger
对象包含一个有两个元素的嵌套列表：
- 一个 integer 包含值 123
- 一个包含两个元素的嵌套列表：
i. 一个 integer 包含值 456
ii. 一个包含一个元素的嵌套列表
a. 一个 integer 包含值 789
思路
乍一看题目看不太懂，翻了翻题解才懂得本题实际上使用括号匹配的思想。
题解
# """ # This is the interface that allows for creating nested lists. # You should not implement it, or speculate about its implementation # """ #class NestedInteger: # def __init__(self, value=None): # """ # If value is not specified, initializes an empty list. # Otherwise initializes a single integer equal to value. # """ # # def isInteger(self): # """ # @return True if this NestedInteger holds a single integer, rather than a nested list. # :rtype bool # """ # # def add(self, elem): # """ # Set this NestedInteger to hold a nested list and adds a nested integer elem to it. # :rtype void # """ # # def setInteger(self, value): # """ # Set this NestedInteger to hold a single integer equal to value. # :rtype void # """ # # def getInteger(self): # """ # @return the single integer that this NestedInteger holds, if it holds a single integer # Return None if this NestedInteger holds a nested list # :rtype int # """ # # def getList(self): # """ # @return the nested list that this NestedInteger holds, if it holds a nested list # Return None if this NestedInteger holds a single integer # :rtype List[NestedInteger] # """ class Solution: def deserialize(self, s: str) -> NestedInteger: if s[0] != '[': return NestedInteger(int(s)) stack, num, f = [], 0, False for i, j in enumerate(s): if j == '-': f = True elif j.isdigit(): num = num * 10 + int(j) elif j == '[': stack.append(NestedInteger()) elif j in ',]': if s[i-1].isdigit(): if f: num = -num stack[-1].add(NestedInteger(num)) if j == ']' and len(stack) > 1: stack[-2].add(stack.pop()) num, f = 0, False return stack.pop()
