Leetcode-954 Array of Doubled Pairs(二倍数对数组)

 1 class Solution
 2 {
 3     public:
 4         bool canReorderDoubled(vector<int>& A)
 5         {
 6             if(A.empty())
 7                 return true;
 8             sort(A.begin(),A.end());
 9             int zcnt = 0;
10             int sz = A.size();
11             for(int i = 0; i < sz; i ++)
12             {
13                 if(A[i]>0)
14                 {
15                     int pos1 = lower_bound(A.begin(),A.end(),A[i]*2)-A.begin();
16                     if(pos1==A.size()||A[pos1]!=2*A[i])
17                         return false;
18                     A.erase(A.begin()+pos1);
19                     sz --;
20                 }
21                 else if(A[i]<0)
22                 {
23                     int pos2 = lower_bound(A.begin(),A.end(),A[i]/2)-A.begin();
24                     if(pos2==A.size()||A[pos2]!=A[i]/2)
25                         return false;
26                     A.erase(A.begin()+pos2);
27                     sz --;
28                 }
29                 else if(A[i]==0)
30                     zcnt ++;
31             }
32             return (zcnt%2)==0;
33         }
34 };