Airbnb Interview - Nested Integer List Parser

实现一个mini parser, 输入是以下格式的string:"324" or"[123,456,[788,799,833],[[]],10,[]]"
要求输出:324 or [123,456,[788,799,833],[[]],10,[]].
也就是将字符串转换成对应的格式的数据.

输入一个数组的字符串, 要返回一个数组, 里面每一个元素是要么一个整数, 要么是一个数组.

但是注意数组可以多层嵌套. 

 

Solution:

public class NestedIntList {

	private int value;
	private List<NestedIntList> intList;
	private boolean isNumber;
	
	public NestedIntList(int v) {
		this.value = v;
		this.isNumber = true;
	}
	
	public NestedIntList() {
		this.intList = new ArrayList<>();
		this.isNumber = false;
	}
	
	public void add(NestedIntList l) {
		intList.add(l);
	}
	
	public static NestedIntList fromString(String s) {
		if(!s.startsWith("[")) {
			return new NestedIntList(Integer.parseInt(s));
		}
		NestedIntList result = null;
		Stack<NestedIntList> stack = new Stack<>();
		int i = 0, left = 1;
		while(i < s.length()) {
			char c = s.charAt(i);
			if(c == '[') {
				NestedIntList num = new NestedIntList();
				if(!stack.isEmpty()) {
					stack.peek().add(num);
				}
				stack.push(num);
				left = i+1;
			} else if(c == ',' || c == ']') {
				if(left != i) {
					int v = Integer.parseInt(s.substring(left, i));
					NestedIntList num = new NestedIntList(v);
					stack.peek().add(num);
				}
				left = i+1;
				if(c == ']') result = stack.pop();
			} 
			i++;
		}
		return result;
	}
	
	public String toString() {
		if(isNumber) {
			return ""+value;
		} else {
			return intList.toString();
		}
	}
	
	public static void main(String[] args) {
		NestedIntList list = NestedIntList.fromString("[123,456,[788,799,833],[[]],10,[]]");
		System.out.println(list);
	}
}