fork download
copy 
  1. /*
  2.   Copyright 2011 Marek "p2004a" Rusinowski
  3.   Matrix multiplication (simplest way)
  4. */
  5. #include <cstdio>
  6. #include <cstring>
  7.  
  8. const int cmod = 1000000007;
  9. int n;
  10.  
  11. int *multiply(int *l, int *r) {
  12.   int *res = new int [n * n];
  13.   for (int i = 0; i < n; ++i) {
  14.     for (int k = 0; k < n; ++k) {
  15.       for (int j = 0; j < n; ++j) {
  16.         *(res + n * i + j) += *(l + n * i + k) * *(r + n * k + j) % cmod;
  17.         *(res + n * i + j) %= cmod;
  18.       }
  19.     }
  20.   }
  21.   return res;
  22. }
  23.  
  24. void read_matrix(int *t) {
  25.   for (int i = 0; i < n; ++i) {
  26.     for (int j = 0; j < n; ++j) {
  27.       scanf("%d", t + n * i + j);
  28.     }
  29.   }
  30. }
  31.  
  32. int main() {
  33.   scanf("%d", &n);
  34.   int *a = new int [n * n], *b = new int [n * n];
  35.   read_matrix(a);
  36.   read_matrix(b);
  37.   int *res = multiply(a, b);
  38.   for (int i = 0; i < n; ++i) {
  39.     for (int j = 0; j < n; ++j) {
  40.       printf("%3d ", *(res + n * i + j));
  41.     }
  42.     printf("\n");
  43.   }
  44.   delete a;
  45.   delete b;
  46.   return 0;
  47. }
  48.  
stdin
copy 
2   
2 1
1 1

2 1
1 1
compilation info 
prog.cpp: In function ‘void read_matrix(int*)’:
prog.cpp:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result
prog.cpp: In function ‘int main()’:
prog.cpp:33: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result
stdout
copy 
  5   3 
  3   2
https://ideone.com/H4S3j
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!