1.4

1/homework/exp1/exp1_4.asm

@@ -0,0 +1,35 @@
+.data
+
+.text
+main:
+    li $v0, 5 # read in
+    syscall
+    move $s0, $v0 # s0 is the n
+    move $a0, $s0 # set the first call arg as n
+    jal hanoi # call proc
+    move $a0, $v0 # print out
+    li $v0, 1
+    syscall
+    li $v0, 17
+    syscall
+
+hanoi:
+    li $t0, 1
+    ble $a0, $t0, hanoi_bottom # if n <= 1, return
+    j hanoi_recur
+hanoi_bottom:
+    li $v0, 1 # return 1
+    jr $ra
+hanoi_recur:
+    subi $sp, $sp, 8 # move sp down by 2 word
+    sw $s0, 4($sp) # first word is the n in caller
+    sw $ra, 0($sp) # second word is the return addr of this callee
+    move $s0, $a0
+    subi $a0, $s0, 1
+    jal hanoi
+    sll $v0, $v0, 1 # hanoi(n - 1) * 2
+    ori $v0, $v0, 1 # hanoi(n - 1) * 2 + 1
+    lw $s0, 4($sp) # reverse s0
+    lw $ra, 0($sp) # reverse ra
+    addi $sp, $sp, 8
+    jr $ra