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385. Mini Parser

2022-08-03 21:27:00 【51CTO】

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.
      
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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.
      
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       /**
       
 * // This is the interface that allows for creating nested lists.
       
 * // You should not implement it, or speculate about its implementation
       
 * public interface NestedInteger {
       
 *     // Constructor initializes an empty nested list.
       
 *     public NestedInteger();
       
 *
       
 *     // Constructor initializes a single integer.
       
 *     public NestedInteger(int value);
       
 *
       
 *     // @return true if this NestedInteger holds a single integer, rather than a nested list.
       
 *     public boolean isInteger();
       
 *
       
 *     // @return the single integer that this NestedInteger holds, if it holds a single integer
       
 *     // Return null if this NestedInteger holds a nested list
       
 *     public Integer getInteger();
       
 *
       
 *     // Set this NestedInteger to hold a single integer.
       
 *     public void setInteger(int value);
       
 *
       
 *     // Set this NestedInteger to hold a nested list and adds a nested integer to it.
       
 *     public void add(NestedInteger ni);
       
 *
       
 *     // @return the nested list that this NestedInteger holds, if it holds a nested list
       
 *     // Return null if this NestedInteger holds a single integer
       
 *     public List<NestedInteger> getList();
       
 * }
       
 */
       
class 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;
       
    }
       
}
      
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本文为[51CTO]所创，转载请带上原文链接，感谢
https://blog.51cto.com/u_15740726/5541903

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