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  1.  
  2. /*
  3.   Copyright 2011 Marek "p2004a" Rusinowski
  4.   Matrix multiplication (class matrix)
  5. */
  6. #include <cstdio>
  7. #include <cstring>
  8. #include <cassert>
  9.  
  10. class Matrix {
  11.  private:
  12.   static const int cmod = 1000000007;
  13.   int n_;
  14.   int *t_;
  15.  
  16.  public:
  17.   Matrix(int n) : n_(n), t_(new int [n_ * n_]) {}
  18.  
  19.   Matrix(int n, const int *t) : n_(n), t_(new int [n_ * n_]) {
  20.     memcpy(t_, t, sizeof(int) * n_ * n_);
  21.   }
  22.  
  23.   Matrix(const Matrix &obj) : n_(obj.n_), t_(new int [n_ * n_]) {
  24.     memcpy(t_, obj.t_, sizeof(int) * n_ * n_);
  25.   }
  26.  
  27.   ~Matrix() {
  28.     delete t_;
  29.   }
  30.  
  31.   Matrix &operator=(const Matrix &obj) {
  32.     if (&obj == this) {
  33.       return *this;
  34.     }
  35.     if (obj.n_ != n_) {
  36.       delete t_;
  37.       n_ = obj.n_;
  38.       t_ = new int [n_ * n_];
  39.     }
  40.     memcpy(t_, obj.t_, sizeof(int) * n_ * n_);
  41.     return *this;
  42.   }
  43.  
  44.   const Matrix operator*(const Matrix &obj) {
  45.     assert(obj.n_ == n_);
  46.     Matrix res(n_);
  47.     for (int i = 0; i < n_; ++i) {
  48.       for (int k = 0; k < n_; ++k) {
  49.         for (int j = 0; j < n_; ++j) {
  50.           *(res.t_ + n_ * i + j) += *(t_ + n_ * i + k) * *(obj.t_ + n_ * k + j) % cmod;
  51.           *(res.t_ + n_ * i + j) %= cmod;
  52.         }
  53.       }
  54.     }
  55.     return res;
  56.   }
  57.  
  58.   Matrix &operator*=(const Matrix &obj) {
  59.     (*this) = (*this) * obj;
  60.     return *this;
  61.   }
  62.  
  63.   const int *operator[](int i) {
  64.     return t_ + n_ * i;
  65.   }
  66. };
  67.  
  68. void read_matrix(int n, int *t) {
  69.   for (int i = 0; i < n; ++i) {
  70.     for (int j = 0; j < n; ++j) {
  71.       scanf("%d", t + n * i + j);
  72.     }
  73.   }
  74. }
  75.  
  76. int main() {
  77.   int n;
  78.   scanf("%d", &n);
  79.   int *a = new int [n * n], *b = new int [n * n];
  80.   read_matrix(n, a);
  81.   read_matrix(n, b);
  82.   Matrix A(n, a), B(n, b);
  83.   A *= B;
  84.   for (int i = 0; i < n; ++i) {
  85.     for (int j = 0; j < n; ++j) {
  86.       printf("%3d ", A[i][j]);
  87.     }
  88.     printf("\n");
  89.   }
  90.   delete a;
  91.   delete b;
  92.   return 0;
  93. }
  94.  
stdin
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2

2 1 
1 1

2 1
1 1
compilation info 
prog.cpp: In function ‘void read_matrix(int, int*)’:
prog.cpp:71: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result
prog.cpp: In function ‘int main()’:
prog.cpp:78: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result
stdout
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  5   3 
  3   2
https://ideone.com/tTzn1
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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