LintCode: Cosine Similarity

 1 class Solution {
 2 public:
 3     /**
 4      * @param A: An integer array.
 5      * @param B: An integer array.
 6      * @return: Cosine similarity.
 7      */
 8     double cosineSimilarity(vector<int> A, vector<int> B) {
 9         // write your code here
10         int AB = 0, size;
11         double lenA = 0, lenB = 0;
12         size = A.size();
13         for (int i = 0; i < size; i++) {
14             AB += A[i]*B[i];
15             lenA += A[i]*A[i];
16             lenB += B[i]*B[i];
17         }
18         if (0 == AB && 0 == lenA && 0 == lenB) {
19             return 2;
20         } else {
21             return AB/(sqrt(lenA)*sqrt(lenB));
22         }
23         
24     }
25 };