Leetcode 385. Mini Parser

最新推荐文章于 2019-09-19 11:42:15 发布

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最新推荐文章于 2019-09-19 11:42:15 发布

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本文介绍了一种使用栈解析嵌套整数列表的方法。针对输入的字符串形式的嵌套整数列表，通过解析返回一个 NestedInteger 对象，该对象可以包含单一整数或多个嵌套的整数列表。

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Given a nested list of integers represented as a string, implement a parser to deserialize it.
Each element is either an integer, or a list -- whose elements may also be integers or other lists.
Example 1:
Given s = "324",

You should return a NestedInteger object which contains a single integer 324.

Example 2:

Given s = "[123,[456,[789]]]",

Return a NestedInteger object containing a nested list with 2 elements:

1. An integer containing value 123.
2. A nested list containing two elements:
    i.  An integer containing value 456.
    ii. A nested list with one element:
         a. An integer containing value 789.

// 这道题可以利用栈来解决

class Solution {
public:
	NestedInteger deserialize(string s) {
		if (s.empty()) return NestedInteger();
		if (s[0] != '[') return NestedInteger(std::stoi(s));
		stack<NestedInteger> stk;
		for (int i = 0, j = 0; i < s.size(); ++i){
			if (s[i] == '['){
				stk.push(NestedInteger());
				j = i + 1;
			}
			else if (s[i] == ','){
				if (s[i - 1] >= '0' && s[i - 1] <= '9')
					stk.top().add(NestedInteger(std::stoi(s.substr(j, i - j))));
				j = i + 1;
			}
			else if (s[i] == ']'){
				if (s[i - 1] >= '0' && s[i - 1] <= '9')
					stk.top().add(NestedInteger(std::stoi(s.substr(j, i - j))));
				if (stk.size() > 1){
					NestedInteger & e = stk.top();
					stk.pop();
					stk.top().add(e);
				}
				// may be [123, [456], [789]]
				j = i + 1;
			}
		}
		return stk.top();
	}
};