1 #define _for(i,a,b) for(int i = (a);i < (b);i ++)
 2 class Solution
 3 {
 4     public:
 5         int f(int len)
 6         {
 7             int sum = 0;
 8             len -= 2;
 9             _for(i,1,len+1)
10             sum += i;
11             return sum;
12         }
13         int
 
 numberOfArithmeticSlices(vector<int>& A)
14         {
15             int cur = 0;
16             if(A.size()<2)
17                 return 0;
18 
19             int rnt = 0;
20             _for(i,0,A.size())
21             {
22                 if(!cur&&A[i]-A[i+1]==A[i+1]-A[i+2
 
])
23                 {
24                     cur = 3;
25                     i += 2;
26                 }
27                 else if(cur&&A[i]-A[i-1]==A[i-1]-A[i-2])
28                     cur ++;
29                 else
30                 {
31                     rnt += f(cur);
32
 
                     cur = 0;
33                     if(!cur&&A[i]-A[i+1]==A[i+1]-A[i+2])
34                     {
35                         cur = 3;
36                         i += 2;
37                     }
38                 }
39             }
40             rnt += f(cur);
41             return rnt;
42         }
43 };

Leetcode-413 Arithmetic Slices(等差數列劃分)