cosineSimilarity

最新推荐文章于 2024-08-14 18:40:11 发布

zjj2015

最新推荐文章于 2024-08-14 18:40:11 发布

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本文介绍了一种衡量两个向量间相似度的方法——余弦相似度，并提供了详细的计算公式及其实现代码。当两个向量位于同一内积空间时，通过计算它们之间的夹角余弦值来评估相似程度。

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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:

/media/problem/cosine-similarity.png

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]).

class Solution {
    /**
     * @param A: An integer array.
     * @param B: An integer array.
     * @return: Cosine similarity.
     */
    public double cosineSimilarity(int[] A, int[] B) {
        // write your code here
        int ab = 0;
        double aa = 0.0;
        double bb = 0.0;
        if(A.length != B.length) return 2.0000;

        if(A.length==1 && A[0]==0 || B.length==1 && B[0]==0) 
            return 2.0000;
        for(int i=0;i<A.length;i++){
            ab += A[i] * B[i];
            aa += A[i] * A[i];
            bb += B[i] * B[i];
        }
        if(aa==0 || bb==0) return 2.0000;
        aa = Math.sqrt(aa);
        bb = Math.sqrt(bb);
        return ab/(aa*bb);
    }
}