C++アルゴリズムのマトリックスの部分操作

#include 
#include 
using namespace std;
typedef vector> MATRIX;
typedef vector MATRIX_CHILD;
typedef vector> ACCESS_MATRIX;
typedef vector ACCESS_MATRIX_CHILD;
MATRIX matrix_power(MATRIX,unsigned int);
MATRIX matrix_mul(MATRIX,MATRIX);
ACCESS_MATRIX  matrix_access(MATRIX,unsigned int);
ACCESS_MATRIX matrix_access(ACCESS_MATRIX,unsigned int);
ACCESS_MATRIX matrix_access_mul(ACCESS_MATRIX,ACCESS_MATRIX);
int main(){
	MATRIX arr{{1,2},{3,4}};
	auto y=matrix_power(arr,3);
	for(auto x:y){
		for(auto z:x)
			cout<