51nod 1137 矩阵乘法

51nod1137：矩阵乘法


关于矩阵的知识：

• 矩阵乘法

假设上图为矩阵A*B=C：
那么矩阵C中的元素C[i][j]=矩阵A中的第i行与矩阵B中的第j列，对应位置每个值的乘积之和。这句话是矩阵乘法的核心。

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int[][] A = new int[n][n];
		int[][] B = new int[n][n];
		int[][] C = new int[n][n];
		for (int i = 0; i < n; i++) {// 输入矩阵A
			for (int j = 0; j < n; j++) {
				A[i][j] = in.nextInt();
			}
		}
		for (int i = 0; i < n; i++) {// 输入矩阵B
			for (int j = 0; j < n; j++) {
				B[i][j] = in.nextInt();
			}
		}
		for (int i = 0; i < n; i++) {// c1的行
			for (int j = 0; j < n; j++) {// c2的列
				for (int k = 0; k < n; k++) {// k代表矩阵A的列的同时也代表矩阵B的行
					C[i][j] += A[i][k] * B[k][j];// 计算矩阵C
				}
			}
		}
		for (int i = 0; i < n; i++) {// 打印矩阵C
			for (int j = 0; j < n; j++) {
				System.out.print(C[i][j] + " ");
			}
			System.out.println("");
		}
	}
}

总结出模板套用:

package ACM_数学;

import java.util.Scanner;

public class text {
	static int[][] pow2(int A[][], int B[][]) {
		int C[][] = new int[A.length][B.length];
		for (int i = 0; i < C.length; i++) {// 初始化
			for (int j = 0; j < C[0].length; j++) {
				C[i][j] = 0;
			}
		}
		for (int i = 0; i < A.length; i++) {// i矩阵A的行
			for (int j = 0; j < B[0].length; j++) {// j矩阵B的列
				for (int k = 0; k < A.length; k++) {// k代表矩阵A的列的同时也代表矩阵B的行
					C[i][j] += A[i][k] * B[k][j];
				}
			}
		}
		return C;
	}

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int[][] A = new int[n][n];
		int[][] B = new int[n][n];
		int[][] C = new int[n][n];
		for (int i = 0; i < n; i++) {// 输入矩阵A
			for (int j = 0; j < n; j++) {
				A[i][j] = in.nextInt();
			}
		}
		for (int i = 0; i < n; i++) {// 输入矩阵B
			for (int j = 0; j < n; j++) {
				B[i][j] = in.nextInt();
			}
		}
		C = pow2(A, B);
		for (int i = 0; i < n; i++) {// 打印矩阵C
			for (int j = 0; j < n; j++) {
				System.out.print(C[i][j] + " ");
			}
			System.out.println("");
		}
	}
}