原题链接在这里：

题目：

Given two  A and B, return the result of AB.

You may assume that A's column number is equal to B's row number.

Example:

A = [  [ 1, 0, 0],  [-1, 0, 3]]B = [  [ 7, 0, 0 ],  [ 0, 0, 0 ],  [ 0, 0, 1 ]]     |  1 0 0 |   | 7 0 0 |   |  7 0 0 |AB = | -1 0 3 | x | 0 0 0 | = | -7 0 3 |                  | 0 0 1 |

题解：

按照两个矩阵相乘的公式计算结果.

Time Complexity: O(m*n*o). m = A.length, n = A[0].length, o = B[0].length.

Space: O(1). regardless res.

AC Java:

1 class Solution { 2     public int[][] multiply(int[][] A, int[][] B) { 3         int m = A.length; 4         int n = A[0].length; 5         int o = B[0].length; 6          7         int [][] res = new int[m][o]; 8         for(int i = 0; i