[leetCode刷题笔记]385. Mini Parser

/** * // 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(); * } */public class Solution {    public NestedInteger deserialize(String s) {        if (s.isEmpty()) {            return null;        }        if (s.charAt(0) != '[') {            return new NestedInteger(Integer.valueOf(s));        }        Stack<NestedInteger> stack = new Stack<NestedInteger>();        NestedInteger curr = null;        int l = 0;        for (int i = 0; i < s.length(); i++) {            if (s.charAt(i) == '[') {                if (curr != null) {                    stack.push(curr);                }                curr = new NestedInteger();                l = i + 1;            }            else if (s.charAt(i) == ']') {                String val = s.substring(l , i);                if (!val.isEmpty()) {                    curr.add(new NestedInteger(Integer.valueOf(val)));                }                if (!stack.isEmpty()) {                    NestedInteger pop = stack.pop();                    pop.add(curr);                     curr = pop;                }                l = i + 1;            }            else if (s.charAt(i) == ',') {                if (s.charAt(i - 1) != ']') {                    String num = s.substring(l, i);                    curr.add(new NestedInteger(Integer.valueOf(num)));                                    }                l = i + 1;            }         }        return curr;    }}