TOP > 数学 行列
行列演算(Matrix)
説明
行列を扱うためのライブラリ。
計算量
- 和, 差: $O(N^2)$
- 積: $O(N^3)$
- 行列累乗: $O(N^3 \log k)$
- 行列式(determinant): $O(N^3)$
実装例
template< class T >
struct Matrix {
vector< vector< T > > A;
Matrix() {}
Matrix(size_t n, size_t m) : A(n, vector< T >(m, 0)) {}
Matrix(size_t n) : A(n, vector< T >(n, 0)) {};
size_t height() const {
return (A.size());
}
size_t width() const {
return (A[0].size());
}
inline const vector< T > &operator[](int k) const {
return (A.at(k));
}
inline vector< T > &operator[](int k) {
return (A.at(k));
}
static Matrix I(size_t n) {
Matrix mat(n);
for(int i = 0; i < n; i++) mat[i][i] = 1;
return (mat);
}
Matrix &operator+=(const Matrix &B) {
size_t n = height(), m = width();
assert(n == B.height() && m == B.width());
for(int i = 0; i < n; i++)
for(int j = 0; j < m; j++)
(*this)[i][j] += B[i][j];
return (*this);
}
Matrix &operator-=(const Matrix &B) {
size_t n = height(), m = width();
assert(n == B.height() && m == B.width());
for(int i = 0; i < n; i++)
for(int j = 0; j < m; j++)
(*this)[i][j] -= B[i][j];
return (*this);
}
Matrix &operator*=(const Matrix &B) {
size_t n = height(), m = B.width(), p = width();
assert(p == B.height());
vector< vector< T > > C(n, vector< T >(m, 0));
for(int i = 0; i < n; i++)
for(int j = 0; j < m; j++)
for(int k = 0; k < p; k++)
C[i][j] = (C[i][j] + (*this)[i][k] * B[k][j]);
A.swap(C);
return (*this);
}
Matrix &operator^=(long long k) {
Matrix B = Matrix::I(height());
while(k > 0) {
if(k & 1) B *= *this;
*this *= *this;
k >>= 1LL;
}
A.swap(B.A);
return (*this);
}
Matrix operator+(const Matrix &B) const {
return (Matrix(*this) += B);
}
Matrix operator-(const Matrix &B) const {
return (Matrix(*this) -= B);
}
Matrix operator*(const Matrix &B) const {
return (Matrix(*this) *= B);
}
Matrix operator^(const long long k) const {
return (Matrix(*this) ^= k);
}
friend ostream &operator<<(ostream &os, Matrix &p) {
size_t n = p.height(), m = p.width();
for(int i = 0; i < n; i++) {
os << "[";
for(int j = 0; j < m; j++) {
os << p[i][j] << (j + 1 == m ? "]\n" : ",");
}
}
return (os);
}
T determinant() {
Matrix B(*this);
assert(width() == height());
T ret = 1;
for(int i = 0; i < width(); i++) {
int idx = -1;
for(int j = i; j < width(); j++) {
if(B[j][i] != 0) idx = j;
}
if(idx == -1) return (0);
if(i != idx) {
ret *= -1;
swap(B[i], B[idx]);
}
ret *= B[i][i];
T vv = B[i][i];
for(int j = 0; j < width(); j++) {
B[i][j] /= vv;
}
for(int j = i + 1; j < width(); j++) {
T a = B[j][i];
for(int k = 0; k < width(); k++) {
B[j][k] -= B[i][k] * a;
}
}
}
return (ret);
}
};