Java实现-余弦相似度

最新推荐文章于 2025-05-24 21:11:25 发布

Narasimha_Karumanchi

最新推荐文章于 2025-05-24 21:11:25 发布

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分类专栏：斩杀LintCode All in One LintCode 文章标签： LintCode余弦相似度

本文链接：https://blog.youkuaiyun.com/qq_14927217/article/details/75095439

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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Java实现代码。当两个向量维度相同时，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:

cosine-similarity

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]).

您在真实的面试中是否遇到过这个题？

Yes

样例

给出 A = [1, 2, 3], B = [2, 3 ,4].

返回 0.9926.

给出 A = [0], B = [0].

返回 2.0000

import java.text.*;
class Solution {
    /**
     * @param A: An integer array.
     * @param B: An integer array.
     * @return: Cosine similarity.
     */
   public static double cosineSimilarity(int[] A, int[] B){
		if(A.length!=B.length){
			return 2.0000;
		}
		if(A==null||B==null){
			return 2.0000;
		}
		long fenzi=0;
		for(int i=0;i<A.length;i++){
			fenzi+=A[i]*B[i];
		}
		long left=0;
		long right=0;
		for(int i=0;i<A.length;i++){
			left+=A[i]*A[i];
			right+=B[i]*B[i];
		}
		if(left*right==0){
			return 2.0000;
		}
		double result=fenzi/Math.sqrt(left*right);
		DecimalFormat df=new DecimalFormat("#.####");
		return Double.parseDouble(df.format(result));
	}

}