2.3-2

分治排序無哨兵位僞代碼：

MERGE(A,p,q,r)
    n1 <- q-p+1
    n2 <- r-q;
    create arrays L[1...n1] and R[1...n2]
    for i <- 1 to n1
        do L[i] <- A[p+i-1]
    for j <- 1 to n2
        do R[j] <- A[q+j]
    m1 <- n1
    m2 <- n2
    i <- 1
    j <- 1
    for k <- p to r
        do if m1 equal 0
           then for j <- j to n2
                do if k < r
                    then A[k] <- R[j]
                         j <- j+1
                         k <- k+1
                continue
            if m2 equal 0
            then for i <- i to n1
                do if k < r
                    then A[k] <- L[i]
                         i <- i+1
                         k <- k+1
                continue
            if L[i] <= R[j]
            then A[k] <- L[i]
                 i <- i+1
                 m1 <- m1-1
            else A[k] <- R[j]
                 j <- j+1
                 m2 <- m2-1