385. Mini Parser

最新推荐文章于 2019-02-24 00:35:57 发布

原创最新推荐文章于 2019-02-24 00:35:57 发布 · 284 阅读

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本文介绍了一种处理嵌套整数序列的算法，重点在于如何正确区分空集与链表，并通过修改代码来实现这一目标。通过对输入字符串的逐字符分析，能够构造出正确的嵌套整数结构。

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采用这种方式，在一些奇奇怪怪的样例上会出错，神烦的样例。主要错出现在对空集合的判断上，无法知道这到底是一个空集，还是个链表。本想通过逗号的位置判断，但还是会出错。于是在一开始就对是否为空集进行判断，于是修改代码：

 if(s[i]=='['||s[i]==',')
 {
     if(s[i+1]==']')
     {
          NestedInteger num;
          nums.push(num);
          i+=2;
     }
     else
          signal.push(s[i++]);
     }
}

/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * class NestedInteger {
 *   public:
 *     // Constructor initializes an empty nested list.
 *     NestedInteger();
 *
 *     // Constructor initializes a single integer.
 *     NestedInteger(int value);
 *
 *     // Return true if this NestedInteger holds a single integer, rather than a nested list.
 *     bool isInteger() const;
 *
 *     // Return the single integer that this NestedInteger holds, if it holds a single integer
 *     // The result is undefined if this NestedInteger holds a nested list
 *     int getInteger() const;
 *
 *     // Set this NestedInteger to hold a single integer.
 *     void setInteger(int value);
 *
 *     // Set this NestedInteger to hold a nested list and adds a nested integer to it.
 *     void add(const NestedInteger &ni);
 *
 *     // Return the nested list that this NestedInteger holds, if it holds a nested list
 *     // The result is undefined if this NestedInteger holds a single integer
 *     const vector<NestedInteger> &getList() const;
 * };
 */
class Solution {
public:
    NestedInteger deserialize(string s) {
        stack<NestedInteger> nums;
        stack<char> signal;

        int i=0;
        while(i<s.size())
        {
            if(s[i]=='['||s[i]==',')
            {
                if(s[i+1]==']')
                {
                    NestedInteger num;
                    nums.push(num);
                    i+=2;
                }
                else
                    signal.push(s[i++]);
            }
            else if(s[i]>='0'&&s[i]<='9')
            {
                int temp=0;
                while(i<s.size()&&s[i]>='0'&&s[i]<='9')
                    temp=temp*10+s[i++]-'0';

                NestedInteger num(temp);
                nums.push(num);
                //cout<<temp<<endl;
            }
            else if(s[i]=='-')
            {
                int temp=0;
                i++;
                while(i<s.size()&&s[i]>='0'&&s[i]<='9')
                    temp=temp*10+s[i++]-'0';
                temp=-temp;
                NestedInteger num(temp);
                nums.push(num);
            }
            else if(s[i]==']')
            {
                stack<NestedInteger> temp;

                if(!nums.empty())
                {
                    temp.push(nums.top());
                    nums.pop();
                }

                while(signal.top()==',')
                {
                    temp.push(nums.top());
                    nums.pop();
                    signal.pop();
                }
                signal.pop();

                NestedInteger num;
                while(!temp.empty())
                {
                    num.add(temp.top());
                    temp.pop();
                }
                nums.push(num);
                i++;
            }


        }

        return nums.top();
    }
};