csr.cpp

#include <algorithm> 
#include <iostream> 
#include <vector> 
using namespace std; 
  
typedef std::vector<int> vi; 
  
typedef vector<vector<int> > matrix; 
  
void printMatrix(const matrix& M) 
{ 
    int m = M.size(); 
    int n = M[0].size(); 
    for (int i = 0; i < m; i++) { 
        for (int j = 0; j < n; j++)  
            cout << M[i][j] << " ";         
        cout << endl; 
    } 
} 
  
void printVector(const vi& V, char* msg) 
{ 
    cout << msg << "[ "; 
    for_each(V.begin(), V.end(), [](int a) { 
        cout << a << " "; 
    }); 
    cout << "]" << endl; 
} 
  
void sparesify(const matrix& M) 
{ 
    int m = M.size(); 
    int n = M[0].size(), i, j; 
    vi A;          // Holds non-zero values 
    vi JA;         // Holds column indexes
    vi IA = { 0 }; // IA holds number of zeros until ith row.
    int NNZ = 0; 
  
    for (i = 0; i < m; i++) { 
        for (j = 0; j < n; j++) { 
            if (M[i][j] != 0) { 
                A.push_back(M[i][j]); 
                JA.push_back(j); 
   
                NNZ++;
            } 
        } 
        IA.push_back(NNZ); 
    } 
  
    printVector(A, (char*)"A = "); 
    printVector(IA, (char*)"IA = "); 
    printVector(JA, (char*)"JA = "); 
} 
  
int main() 
{ 
    matrix M = { 
        { 0, 0, 0, 0, 1 }, 
        { 5, 8, 0, 0, 0 }, 
        { 0, 0, 3, 0, 0 }, 
        { 0, 6, 0, 0, 1 }, 
    }; 
  
    sparesify(M); 
  
    return 0; 
}