蓝桥杯-矩阵乘法

提交代码

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		long[][] a = new long[n][n];//用int容易越界，所以用long
		long[][] b = new long[n][n];
		for(int i = 0;i<n;i++) {
			for(int j = 0;j<n;j++) {
				a[i][j] = b[i][j] = sc.nextLong();//写出两个矩阵，然后相乘
			}
		}
		if(m == 0) {//矩阵得0次幂等于单位矩阵E
			for(int i = 0;i<n;i++) {
				for(int j = 0;j<n;j++) {
					if(i == j) {
						System.out.print(1+" ");
					}
					else
					{
						System.out.print(0+" ");
					}
				}
				System.out.println();
			}
		}
		else if(m == 1) {//输出自己
			for(int i = 0;i<n;i++) {
				for(int j = 0;j<n;j++) {
					System.out.print(a[i][j]+" ");
				}
			System.out.println();
			}
		}
		else {
		
			for(int i = 1;i<m;i++) {
				long[][] db = new long[n][n]; //临时矩阵
				for(int j = 0;j<n;j++) {
					for(int k = 0;k<n;k++) {
						for(int l = 0;l<n;l++) {
							db[j][k] +=a[j][l]*b[l][k]; //核心公式
						}						
					}
				}
				b = db;//将db赋值给b，下次幂运算就用二次乘一次达到递增
			}
			//输出
			for(int i = 0;i<n;i++) {
				for(int j = 0;j<n;j++) {
					System.out.print(b[i][j]+" ");
				}
			System.out.println();
			}
		}
	}
}