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// Source : https://leetcode.com/problems/mini-parser/

// Author : Hao Chen

// Date : 2016-08-24

/***************************************************************************************

*

* 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.

*

* 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.

***************************************************************************************/

/**

* // 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) {

if (s.size()==0) return NestedInteger();

int pos = 0;

if (s[pos]!='[') return atoni(s, pos);

return helper(s, ++pos);

}

private:

NestedInteger helper(string& s, int& pos) {

NestedInteger ni;

while ( s[pos] != ']' && pos < s.size() ) {

if (s[pos]=='-' || isnum(s[pos])){

ni.add(atoni(s, pos));

}else if (s[pos] == '[') {

pos++;

ni.add(helper(s, pos));

}else {

pos++;

}

}

pos++;

return ni;

}

NestedInteger atoni(string& s, int& pos) {

int sign = 1;

int num = 0;

if (s[pos]=='-') {

sign = -1;

pos++;

}

for (; pos < s.size(); pos++) {

if (isnum(s[pos])) {

num = num * 10 + s[pos] - '0';

}else{

break;

}

}

return NestedInteger(sign * num);

}

bool isnum(char& c) {

return (c >='0' && c <='9');

}

};