[C++] 두 행렬의 곱 구하기(3x3)

 

실습 9-4번 문제

두 행렬의 곱 구하기(3x3)

 

void randomNumbers(int inumbers[][3], int rowSize);
void multiplyMatrix(int a[][3], int b[][3], int c[][3], int rowSize);
void printArray(int num[][3], int rowSize);

 

 

//
//  main.cpp
//
//  Created by yeonsu on 2022/06/14.
//

// 난수(0~9)발생 시키기, 숫자의 출현 빈도수 세기(4행 3열)

#include <iostream>
#include <ctime>        //rand 함수
#include <iomanip>

using namespace std;

const int ROW = 4;
const int COL = 3;

void randomNumbers(int inumbers[][3], int rowSize);
void multiplyMatrix(int a[][3], int b[][3], int c[][3], int rowSize);
void printArray(int num[][3], int rowSize);
    
    
int main(){
    
    int a[ROW][COL];
    int b[ROW][COL];
    int c[ROW][COL];

    // 난수 함수 호출
        randomNumbers(a, 3);
        randomNumbers(b, 3);

        // 곱셈 함수 호출
        multiplyMatrix(a, b, c, 3);

        cout << "==================\n";
        printArray(a, 3);
        cout << "==================\n";
        cout << "                  \n";
        cout << "         *         \n";
        cout << "==================\n";
        printArray(b, 3);
        cout << "==================\n";
        cout << "                  \n";
        cout << "         =         \n";
        cout << "==================\n";
        printArray(c, 3);

    return 0;
}

void printArray(int num[][3], int rowSize) {    //2차원 배열 출력

    for (int row = 0; row < rowSize; row++) {
        for (int col = 0; col < COL; col++)
            cout << setw(5) << num[row][col];
        cout << endl;
    }
}

void randomNumbers(int inumbers[][3], int rowSize) {
    for (int row = 0; row < rowSize; row++) {
        for (int col = 0; col < COL; col++)
            inumbers[row][col] = rand() % 10;
    }
}
    void multiplyMatrix(int a[][3], int b[][3], int c[][3], int rowSize) {

        int mul[3][3];

        for (int row = 0; row < rowSize; row++) {
            for (int col = 0; col < 3; col++) {
                c[row][col] = 0;
                for (int x = 0; x < 3; x++) {
                    c[row][col] += a[row][x] * b[x][col];
                }
            }
        }
    }

실행 결과

---

Key Point

    void multiplyMatrix(int a[][3], int b[][3], int c[][3], int rowSize) {

 

        for (int row = 0; row < rowSize; row++) {

            for (int col = 0; col < 3; col++) {

                c[row][col] = 0;  // 초기화 시켜줌

                for (int x = 0; x < 3; x++) {

                c[row][col] += a[row][x] * b[x][col];

                }

            }

        }

    }