# LeetCode – Mini Parser (Java)

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, [, -, ,, ].

For example,

```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.
```

Java Solution

```public NestedInteger deserialize(String s) {   Stack<NestedInteger> stack = new Stack<NestedInteger>(); String temp = "";   for(char c: s.toCharArray()){ switch(c){ case '[': stack.push(new NestedInteger()); //start a new NI break;   case ']': if(!temp.equals("")){ stack.peek().add(new NestedInteger(Integer.parseInt(temp))); //add NI to parent temp=""; }   NestedInteger top = stack.pop(); if(!stack.empty()){ stack.peek().add(top); }else{ return top; }   break;   case ',': if(!temp.equals("")){ stack.peek().add(new NestedInteger(Integer.parseInt(temp)));//add NI to parent temp=""; }   break;   default: temp += c; } }   if(!temp.equals("")){ return new NestedInteger(Integer.parseInt(temp)); }   return null; }```
Category >> Algorithms
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