Merge pull request #42 from sidharthism/master

Added sparse multiplication.

C++/Matrix/sparseMultiplication.cpp

@@ -0,0 +1,113 @@
+#include <iostream>
+
+using namespace std;
+
+#define MAX 50
+typedef int Matrix[100][100];
+
+struct tup {
+   int r;
+   int c;
+   int value;
+};
+
+// Funcion to display sparse matrix
+void displaySp(tup sp[MAX]){
+  for(int i=0;i<=sp[0].value;i++){
+      cout<<" "<<sp[i].r<<" "<<sp[i].c<<" "<<sp[i].value<<"\n";
+  }
+}
+
+// Function to construct sparse matrix
+void constructSparseMatrix(Matrix(a), tup sp[MAX], int m, int n){
+  int k = 1;
+  sp[0].r = m;
+  sp[0].c = n;
+  for(int i = 0;i<m;i++){
+    for(int j=0;j<n;j++){
+      if(a[i][j] != 0){
+        sp[k].r = i;
+        sp[k].c = j;
+        sp[k].value = a[i][j];
+        k++;
+      }
+    }
+  }
+  sp[0].value = k-1;
+  displaySp(sp);
+}
+
+// Function to do multiplication in sparse representation. 
+void spMultiply(tup a[MAX], tup b[MAX], tup prod[MAX]){
+  prod[0].r = a[0].r;
+  prod[0].c = b[0].c;
+  prod[0].value = 0;
+  int flag = 0;
+  int k=0, s=0;
+  for(int i = 1;i<=a[0].value;i++){
+    for(int j=1;j<=b[0].value;j++){
+      flag = 0;
+      if(a[i].c == b[j].r){
+        s = a[i].value * b[j].value;
+        for(int l=1;l<=k;l++){
+           if(prod[l].r == a[i].r && prod[l].c == b[j].c){
+              prod[l].value += s;
+              flag = 1;
+           }
+        }
+        if(flag == 0){
+          k++;
+          prod[k].r = a[i].r;
+          prod[k].c = b[j].c;
+          prod[k].value = s;
+          flag = 1;
+        }
+      }
+    }
+  }
+  prod[0].value = k; // Update size of sum
+}
+
+//Main
+int main() {
+  Matrix A, B;
+  int m, n, p, q;
+  tup spA[MAX], spB[MAX], PROD[MAX];
+
+  // Get the order of A
+  cout<<"\n Enter the order of matrix A : ";
+  cin>>m>>n;
+
+  // Input elements A
+  cout<<"\n Enter the elements of matrix A: ";
+  for(int i=0;i<m;i++){
+    for(int j=0;j<n;j++){
+      cin>>A[i][j];
+    }
+  }
+
+ // Get the order of B
+  cout<<"\n Enter the order of matrix B : ";
+  cin>>p>>q;
+
+  if(n != p){
+    cout<<"\n Cannot perform multiplication... \n";
+    exit(0);
+  }
+
+  // B
+  printf("\n Enter the elements of matrix B: ");
+  for(int i=0;i<p;i++){
+    for(int j=0;j<q;j++){
+      cin>>B[i][j];
+    }
+  }
+  cout<<"\n The sparse matrix representation of A is : \n\n";
+  constructSparseMatrix(A, spA, m, n);
+  cout<<"\n The sparse matrix representation of B is : \n\n";
+  constructSparseMatrix(B, spB, p, q);
+  spMultiply(spA, spB, PROD);
+  cout<<"\n The result of multiplication of matrices, AB, in sparse representation is : \n\n";
+  displaySp(PROD);
+  return 0;
+}