Sparse Matrix Multiplication
Given two sparse matrices 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 |
1 public class Solution { 2 public int[][] multiply(int[][] A, int[][] B) { 3 int mA = A.length, nA = A[0].length, nB = B[0].length; 4 int[][] result = new int[mA][nB]; 5 6 for (int i = 0; i < mA; i++) { 7 for (int j = 0; j < nA; j++) { 8 if (A[i][j] != 0) { 9 for (int k = 0; k < nB; k++) { 10 if (B[j][k] != 0) 11 result[i][k] += A[i][j] * B[j][k]; 12 } 13 } 14 } 15 } 16 return result; 17 } 18 }