@deepreader if A[m/2]>B[n/2] and k>m/2+n/2, then disregard B_left and B[n/2] if A[m/2]>B[n/2] and k<=m/2+n/2, then disregard A_right and A[m/2] if A[m/2]<=B[n/2] and k>m/2+n/2, then disregard A_left and A[m/2] if A[m/2]<=B[n/2] and k<=m/2+n/2, then disregard B_right and B[n/2] 这里怎么理解