当前位置：首页 > news >正文

PageRank算法c++实现

news 2025/8/19 20:29:36

首先用邻接矩阵A表示从页面j到页面i的概率，然后根据公式生成转移概率矩阵

M=（1-d）*Q+d*A 常量矩阵Q=(qi,j),qi,j=1/n

给定点击概率d，等级值初始向量R0，迭代终止条件e；

计算Ri+1=M*Ri；

ei=|Ri+1-Ri|，当ei<=e时输出Ri+1作为最终等级值向量。

#include "fstream"
#include "sstream"
#include <iostream>
#include <set>
#include <vector>using namespace std;int getNum()
{set<int> N;ifstream is("a.txt");int u, v;while (is >> u >> v){N.insert(u);N.insert(v);}return N.size();
}void getPage(vector<vector<int>>& page)     //&
{ifstream is("a.txt");int u, v;while(is>>u>>v){ page[u].push_back(v);}
}void PageRank(vector<vector<int>>&page,int N,double d,double e,int maxIterations)
{//得到Mvector<vector<double>> M(N,vector<double>(N,0.0));for (int i = 0; i < N; i++){if (page[i].size() > 0){for (int j : page[i]){M[j][i]++;           //0/1}for (int j=0;j<N;j++){M[j][i] /= page[i].size();}}else{for (int j : page[i]){M[j][i] = 0;}}}for (int i = 0; i < N; i++){for (int j = 0; j < N; j++){//cout << M[i][j]<<" ";             //正确M[i][j] = d * M[i][j] + (1 - d) * (1.0 / N);//cout << M[i][j] << " ";}}vector<double> pagerank(N, 1.0);while (maxIterations){vector<double> newpagerank(N, 0.0);double dif=0.0;for (int i = 0; i < N; i++){for (int j = 0; j < N; j++){newpagerank[i] += M[i][j] * pagerank[j];}dif+= abs(pagerank[i]-newpagerank[i]);}//cout << dif << endl;pagerank = newpagerank;if (dif < e){//cout << maxIterations<<endl;break;}maxIterations--;}cout << "等级值分别为：" << endl;for (int i = 0; i < N; i++){cout << pagerank[i]<<endl;}
}int main()
{int num = getNum();vector<vector<int>> page(num);getPage(page);double d = 0.85;double e = 0.1;int maxIterations = 100;PageRank(page, num, d, e, maxIterations);}

数据

0 1
0 2
0 3
1 0
1 2
2 3
3 0
3 1

结果