leetcode解题: Mini Parser (385)

发表于 | 分类于

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.

Note: You may assume that the string is well-formed:

String is non-empty.
String does not contain white spaces.
String contains only digits 0-9, [, - ,, ].
Example 1:

1
2
3
Given s = "324",
You should return a NestedInteger object which contains a single integer 324.

Example 2:

1
2
3
4
5
6
7
8
9
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.

解法1： Iterative

这题自己写的stack版本怎么也过不了OJ， 参考了这篇帖子的解法
C++

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
class Solution {
public:
    NestedInteger deserialize(string s) {
        if (s.empty()) return NestedInteger();
        if (s[0] != '[') return NestedInteger(stoi(s));
        stack<NestedInteger> st;
        int start = 1;
        for (int i = 0; i < s.size(); ++i) {
            if (s[i] == '[') {
                st.push(NestedInteger());
                start = i + 1;
            } else if (s[i] == ',' || s[i] == ']') {
                if (i > start) {
                    st.top().add(NestedInteger(stoi(s.substr(start, i - start))));
                }
                start = i + 1;
                if (s[i] == ']') {
                    if (st.size() > 1) {
                        NestedInteger t = st.top(); st.pop();
                        st.top().add(t);
                    }
                }
            }
        }
        return st.top();
    }
};

Java

1