資訊專欄INFORMATION COLUMN
Problem
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.
See wiki: Cosine Similarity
Here is the formula:
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]).
Given A = [1, 2, 3], B = [2, 3 ,4].
Return 0.9926.
Given A = [0], B = [0].
Return 2.0000
class Solution {
public double cosineSimilarity(int[] A, int[] B) {
// write your code here
if (A.length == 0 || B.length == 0 || A.length != B.length) {
return 2;
}
int aa = 0, bb = 0, ab = 0;
for (int i = 0; i < A.length; i++) {
aa += A[i]* A[i];
bb += B[i]* B[i];
ab += A[i]* B[i];
}
if (aa == 0 || bb == 0) return 2;
return ab / (Math.sqrt(aa) * Math.sqrt(bb));
}
}
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