【LeetCode 241】Different Ways to Add Parentheses

(2*(3-(4*5))) = -34
((2*3)-(4*5)) = -14
((2*(3-4))*5) = -10
(2*((3-4)*5)) = -10
(((2*3)-4)*5) = 10

 1 class Solution {
 2 public:
 3 
 4     //string转为int
 5     int getInts(string str)
 6     {
 7         int ret = 0;
 8 
 9         stringstream ss;
10         ss << str;
11         ss >> ret;
12 
13         return ret;
14     }
15 
16     vector<int> rec(vector<int>& num, int start, int ends)
17     {
18         vector<int> vec;
19     
20         if(start == ends)
21         {
22             vec.push_back(num[start]);
23             return vec;
24         }
25     
26         for(int i = start; i <= ends; i++)
27         {
28             if(num[i] == -3)
29             {
30                 vector<int> vecl = rec(num, start, i - 1);
31                 vector<int> vecr = rec(num, i + 1, ends);
32     
33                 vector<int>::iterator itl = vecl.begin();
34                 for(; itl != vecl.end(); itl++)
35                 {
36                     vector<int>::iterator itr = vecr.begin();
37                     for(; itr != vecr.end(); itr++)
38                         vec.push_back((*itl) + (*itr));
39                 }
40             }
41             if(num[i] == -1)
42             {
43                 vector<int> vecl = rec(num, start, i - 1);
44                 vector<int> vecr = rec(num, i + 1, ends);
45     
46                 vector<int>::iterator itl = vecl.begin();
47                 for(; itl != vecl.end(); itl++)
48                 {
49                     vector<int>::iterator itr = vecr.begin();
50                     for(; itr != vecr.end(); itr++)
51                         vec.push_back((*itl) - (*itr));
52                 }
53             }
54             if(num[i] == -4)
55             {
56                 vector<int> vecl = rec(num, start, i - 1);
57                 vector<int> vecr = rec(num, i + 1, ends);
58     
59                 vector<int>::iterator itl = vecl.begin();
60                 for(; itl != vecl.end(); itl++)
61                 {
62                     vector<int>::iterator itr = vecr.begin();
63                     for(; itr != vecr.end(); itr++)
64                         vec.push_back((*itl) * (*itr));
65                 }
66             }
67         }
68         return vec;
69     }
70     
71     vector<int> diffWaysToCompute(string input) {
72         
73         //先把字符串转换为一个int型的数组，符号用负数来表示
74         vector<int> nums;
75         int index = 0;
76         for(int i = 0; i < input.size(); i++)
77         {
78             if(input[i] == ‘+‘ || input[i] == ‘-‘ || input[i] == ‘*‘)
79             {
80                 string str = input.substr(index, i - index);
81                 nums.push_back(getInts(str));
82                 nums.push_back(input[i]-46); //加号转换为-3， 减号转换为-1，乘号为-4
83                 index = i + 1;
84             }
85             if(i == input.size() - 1)
86             {
87                 string str = input.substr(index, input.size() - index);
88                 nums.push_back(getInts(str));
89             }
90         }
91         
92         int len = nums.size();
93         if(len == 0 || len == 1)
94             return nums;
95         
96         vector<int> ret = rec(nums, 0, len - 1);
97         return ret;
98     }
99 };