# 385. Mini Parser

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:

``````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.
``````

``````class Solution {
public:
NestedInteger deserialize(string s) {
if (s.empty()) return NestedInteger();
if (s[0] != '[') return NestedInteger(stoi(s));
if (s.size() <= 2) return NestedInteger();
NestedInteger res;
int start = 1, cnt = 0;
for (int i = 1; i < s.size(); ++i) {
if (cnt == 0 && (s[i] == ',' || i == s.size() - 1)) {
res.add(deserialize(s.substr(start, i - start)));
start = i + 1;
} else if (s[i] == '[') ++cnt;
else if (s[i] == ']') --cnt;
}
return res;
}
};
``````

``````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();
}
};
``````

``````class Solution {
public:
NestedInteger deserialize(string s) {
istringstream in(s);
return deserialize(in);
}
NestedInteger deserialize(istringstream& in) {
int num;
if (in >> num) return NestedInteger(num);
in.clear();
in.get();
NestedInteger list;
while (in.peek() != ']') {
list.add(deserialize(in));
if (in.peek() == ',') {
in.get();
}
}
in.get();
return list;
}
};
``````

Nested List Weight Sum II

Flatten Nested List Iterator

Nested List Weight Sum

https://discuss.leetcode.com/topic/54258/python-c-solutions/3

https://discuss.leetcode.com/topic/54341/iterative-c-using-stack

https://discuss.leetcode.com/topic/54277/short-java-recursive-solution

LeetCode All in One 题目讲解汇总(持续更新中…)

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