Question

我正在为卢卡斯序列实现一个mips程序。用户输入数字n，P和Q，并为V序列选择1，为U序列选择0。我在选择V序列时遇到问题只有在P为1时才返回P所有其他数字。我知道这是我遗漏的一点点，但我一直试图找到它几个小时。任何帮助将不胜感激。

    addi $t1, $s0, 0            # load n into $t1
    addi $t3, $zero, 0          # i = 0

    jal lucasSequence           # go to lucasSequence

end_loop:   
    la $a0, newline             # print a newline \n
    jal printString     

    j main                      # loop to main menu again


############################################# 
# Procedure: lucasSequence                  #   
#############################################
#   - produces the Lucas sequence of the    #
#     first (U) or second (V) order for     #
#     given constants P and Q.              #
#                                           #
#     The procedure produces all numbers    #       
#     in the sequence U or V from n=0       # 
#     up to n=N.                            #
#                                           #
#   - inputs : $a0-integer N                #
#              $a1-constant P               #
#              $a2-constant Q               #
#              $a3-function U (0) or V (1)  #
#   - outputs: none                         #   
#                                           #
#############################################   
lucasSequence:

loop:   
    move $a0, $t3               # n = i
    beq $t3, $t1, end_loop      # if i == n, quit.
    jal lucasSequenceNumber     # print the lucas sequence for N, P, and Q
    addi $t3, $t3, 1            # i++
    move $a0, $v0               # load int to print
    li $v0, 1                   # print int
    syscall                     # print call
    beq $t3, $t1, end_loop      # don't print last comma
    li $a0, ','                 # load comma
    li $v0, 11                  # add to print
    syscall                     # print comma
    li $a0, ' '                 # load space
    li $v0, 11                  # print space
    syscall                     # print call
    j loop                      # repeat until i = n

lucasSequenceNumber: 
    addi $sp, $sp, -8           # room for $ra and one temporary
    sw $ra, 4($sp)              # save $ra
    move $v0, $a0               # pre-load return value as n
    addi $t4, $zero, 1          # t4 =1 
    blt $a0, 2, rt              # if(n < 2) return
    sw $a0, 0($sp)              # save a copy of n
    addi $a0, $a0, -1           # n - 1
    jal lucasSequenceNumber     # lucas(n - 1)
    lw $a0, 0($sp)              # retrieve n
    mul $v0, $v0, $a1           # P*lucas(n-1)
    sw $v0, 0($sp)              # save result of P*lucas(n - 1)
    addi $a0, $a0, -2           # n - 2
    jal lucasSequenceNumber     # lucas(n - 2)
    mul $v0, $v0, $a2           # Q*lucas(n-2)
    lw $v1, 0($sp)              # retrieve P*lucas(n - 1)
    sub $v0, $v1, $v0           # P*lucas(n - 1) + Q*lucas(n - 2)

rt: 
    addi $t4, $zero, 1          # t4 = 1
    beq $a3, $t4, return_V      # user chose option 2
lucas_rt:
    lw $ra, 4($sp)              # restore $ra
    addi $sp, $sp, 8            # restore $sp
    jr $ra                      # back to caller
return_V:
    bgt $a0, $t4, lucas_rt      # if choice V and n > 1, got to return
    beq $a0, $t4, one_v         # if n = 1, go to one_v
    li $a0, 2                   # if n = 0, return 2 
    move $v0, $a0
    j lucas_rt                  # back to caller
one_v:
    addi $a0, $a1, 0            # return P
    move $v0, $a0
    j lucas_rt                  # go to return P call

Answer 1

需要调整one_v函数，使其显示为：

one_v:
    move $a0, $a1
    move $a0, $v0
    j lucas_rt

MIPS：Lucas序列当P为1时，每隔一个数字返回P.

1 个答案: