311. Sparse Matrix Multiplication

    /*
     * 311. Sparse Matrix Multiplication
     * 2016-7-4 by Mingyang
     * 这个题目真的是脑壳进屎了才会用HashMap做。。。。。
     */
    public int[][] multiply(int[][] A, int[][] B) {
        int m = A.length, n = A[0].length, nB = B[0].length;
        int[][] C = new int[m][nB];
        for(int i = 0; i < m; i++) {
            for(int k = 0; k < n; k++) {
                if (A[i][k] != 0) {
                    for (int j = 0; j < nB; j++) {
                        if (B[k][j] != 0) C[i][j] += A[i][k] * B[k][j];
                    }
                }
            }
        }
        return C;   
    }