Cosine Similarity
出处
Cosine similarity is a measure of similarity between two vectors of an inner product space that measures the cosine of the angle between them. The cosine of 0° is 1, and it is less than 1 for any other angle.
Given two vectors A and B with the same size, calculate the cosine similarity.
Return 2.0000 if cosine similarity is invalid (for example A = [0] and B = [0]).
样例
Given A = [1, 2, 3], B = [2, 3 ,4].
Return 0.9926.
Given A = [0], B = [0].
Return 2.0000
Solution
依照题意计算即可
Complexity
时间复杂度 O(n),空间复杂度 O(1)
Code
class Solution {
/**
* @param A: An integer array.
* @param B: An integer array.
* @return: Cosine similarity.
*/
public double cosineSimilarity(int[] A, int[] B) {
if ( A.length != B.length){
return 2.0000;
}
double up = 0.0;
double down1 = 0.0;
double down2 = 0.0;
for (int i = 0; i < A.length; i++){
up += A[i] * B[i];
down1 += A[i] * A[i];
down2 += B[i] * B[i];
}
if (down1 == 0 || down2 == 0){
return 2.0000;
}
return up / (Math.sqrt(down1*down2));
}
}