汇编实践课第二次作业

最新推荐文章于 2023-04-06 20:19:49 发布

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本文通过具体的汇编语言实例，讲解了正负数统计、数组最大值查找、冒泡排序、选择排序、快速排序等基本算法的实现过程，并演示了字符串复制与翻转的方法。

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第二次：1.求正负数的个数 2.求数组最大值 3.冒泡排序 4.选择排序 5.快排核心 6.复制字符串 7.翻转字符串

1.统计正数（负数）的个数内容：DAT开始的单元中存放N个字节有符号数，统计正数的个数存入T0单元中;负数的个数存入T1单元中

INCLUDE Irvine32.inc
.data
	dat db 12,23,-45,54,25,94,0,12,-2,4
	t0 db ?
	t1 db ?
	len dd $-dat
.code
main proc
	lea	edx,dat	
	mov	ecx,len
	call sum
	movsx	eax,byte ptr t0
	call	writeint
	movsx	eax,byte ptr t1
	call	writeint
	exit
main endp

sum proc
again:
	test	byte ptr [edx],80h
	je	plus  ;=0
	inc	t0
	jmp	next
plus:
	inc 	t1
next:
	inc	edx
	loop	again
	ret
sum endp

end main

2.求最大数内容：DAT开始的字单元中存放N个无符号数，求出最大数存入MAX单元中

INCLUDE Irvine32.inc
.data
	dat dw 12,23,45,54,25,94,0,12,2,4
	max1 dw ?
	len dd ($-dat)/2
.code
main proc
	lea	edx,dat	
	mov	ecx,len
	mov	max1,0
	call 	max
	movsx	eax,word ptr max1
	call	writeint
	exit
main endp

max proc
again:
	mov	ax,word ptr [edx]
	cmp	max1,ax
	ja	next
	mov	max1,ax
next:
	add	edx,2
	loop	again
	ret
max endp

end main

部分参考老师

冒泡排序

INCLUDE Irvine32.inc
.data
	arr dd 60,30,40,50,1,70,80,100,90,5
	len dd ($-arr)/4
.code
main proc
	lea	edx,arr
	mov	ecx,len
	call	bubble_sort
	lea	edx,arr
	mov	ecx,len
	call	output
	exit
main endp

bubble_sort proc
	mov	ebx,ecx	;n->ebx
	mov	esi,0	;i->esi
out_loop:
	push	ebx
	sub	ebx,esi
	dec	ebx	;ebx->n-i-1
	mov	edi,0	;edi->j
in_loop:
	cmp	edi,ebx
	jnb	final	;>=结束循环
	mov	eax,[edx + 4 * edi]
	cmp	eax,[edx + 4 * edi + 4]
	jna	next
	xchg	eax,[edx + 4 * edi + 4]	;exchange
	mov	[edx + 4 * edi],eax
next:
	inc	edi	;j++
	jmp	in_loop
final:
	pop	ebx
	inc	esi
	loop	out_loop
	ret
bubble_sort endp

output proc
	mov	ebx,0
again:
	mov	eax,[edx + 4 * ebx]
	call	writeint
	inc	ebx
	mov	al,' '
	call	writechar
	loop	again
	ret
output endp
end main

参考核心

int i, j
for(i = 0;i < n;i++)
{
	for(j = 0;j < n-1-i;j++)
	{
		if(arr[j] > arr[j+1])
		{
			swap(arr[j], arr[j+1])
		}
	} 
}

选择排序

INCLUDE Irvine32.inc
.data
	arr dd 1,4,34,56,845,516
	len dd ($ - arr) / 4
	len1 dd ?
.code
main proc
	mov	edx,offset arr
	mov	ecx,len			;ecx用于loop找最大值
	mov	edi,len			;edi保存最后一个数的位子
	call	select_sort		;排序
	mov	ecx,len			;输出
	call	output
	exit
main endp
;总体思路，先找到max放到最后一个数，然后依次loop
select_sort proc
L1:
	call max			;找最大
	dec	ebx			;最后一步加了1，减回来
	mov	ecx,[edx + 4 * ebx]	;交换
	mov	[edx + 4 * ebx],eax	
	mov	[edx + 4 * esi],ecx
	dec	edi			;最后的位子减1
	mov	ecx,edi			;ecx用于loop找最大值
	cmp	edi,0			;检查是否结束
	ja	L1
	ret
select_sort endp
	;find max.  ebx begin 0 for index 
		   ;eax for max
		   ;esi for max index
		   ;edx for arr'firsr address
max proc 				
	mov	ebx,0
	mov	eax,[edx]
again:
	cmp	eax,[edx + 4 * ebx]
	ja	next
	mov	eax,[edx + 4 * ebx]
	mov	esi,ebx			;esi得知最大数的index
next:
	inc	ebx
	loop 	again
	ret
max endp

output proc
	mov	ebx,0
again1:
	mov	eax,[edx + 4 * ebx]
	call 	writeint
	inc	ebx
	mov	al,' '
	call 	writechar
	loop	again1
	ret
output endp
END main

快排

INCLUDE Irvine32.inc
.data
	arr dd 12,23,45,5,25,94,0,13,2,4
	len dd ($ - arr) / 4
	low1 dd 0
	high1 dd 9
.code
main proc
	lea	edx,arr
	mov	esi,low1
	mov	edi,high1
	mov	eax,[arr + 4 * esi]
	call	par
	exit
main endp

par proc
;edx=a[],esi=low,edi=high,eax=a[low]
out_:
	cmp	esi,edi
	jge	final
in_1:
	cmp	esi,edi
	jge	final
	cmp	[edx + 4 * edi],eax
	jl	final_1
	dec	edi
	jmp 	in_1
	
final_1:
	mov	ebx,[edx + 4 * esi]
	xchg 	ebx,[edx + 4 * edi]
	mov	[edx + 4 * esi],ebx
in_2:
	cmp	esi,edi
	jge	final
	cmp	[edx + 4 * esi],eax
	jg	final_2
	inc	esi
	jmp 	in_2
	
final_2:
	mov	ebx,[edx + 4 * esi]
	xchg 	ebx,[edx + 4 * edi]
	mov	[edx + 4 * esi],ebx

	jmp	out_
final:
	call	output
	ret
par endp

output proc
	mov	ecx,len
	lea	edx,arr
again:
	mov	eax,[edx]
	call	writeint
	add	edx,4
	loop	again
	ret
output endp
end main

参考核心

key = a[low];
while(low < high)
{
	while(low < high && key <= a[high])
	{
		high--;
	}
	swap(a[i],a[j]);
	while(low < high && key >= a[low])
	{
		low++;
	}
	swap(a[i],a[j]);
}

复制字符串

include Irvine32.inc
.data
	arr1 db 'personal_computer',0
	arr2 db  17 dup(?)
	     db 0
.code
main proc
	lea 	esi,arr1
	lea 	edi,arr2
	mov	ecx,sizeof arr1	;esi->edi for ecx
	cld	;标志位
	rep	movsb
	lea	edx,arr2
	call	writestring
	exit
main endp
end main

翻转字符串

include Irvine32.inc
.data
	arr1 db 'personal_computer',0
	arr2 db  17 dup(?)
	     db 0
.code
main proc
	lea 	esi,arr1
	lea 	edi,arr2
	mov	ecx,sizeof arr1	;esi->edi for ecx
	cld	;标志位
	rep	movsb
	mov	ecx,sizeof arr1
	dec	ecx
L:
	mov	al,byte ptr [arr2 + ecx - 1]
	call	writechar
	loop	L
	exit
main endp
end main