C语言与汇编的嵌入式编程：统计字符串中各字符出现的次数
原始C语言：
#include<stdio.h>
void main(){
char str[1024];
char pipei[] = "abcdefghijklmnopqrstuvwxyz";
int count[26]={0};
int i=0,j=0;
scanf("%s",str);
printf("%s\n",str);
for(i=0;i<1024;i++)
{
for(j=0;j<26;j++)
{
if(str[i]==pipei[j])
count[j]+=1;
}
}
for(j=0;j<26;j++)
{
if(count[j]>0)
printf("%c=%d\n",pipei[j],count[j]);
}
}加入汇编后代码：
#include<stdio.h>
void main(){
char str[1024];
char pipei[] = "abcdefghijklmnopqrstuvwxyz";
int count[26]={0};
int i=0,j=0;
scanf("%s",str);
printf("%s\n",str);
//外层循环start
_asm{
mov eax,0 //i=0
mov ecx,1024 //i<1024
loop1:
mov i,eax
push eax
push ecx
};
//printf("%c\t",str[i]);
//内层循环start
_asm{
mov eax,0
mov ecx,26
loop2:
mov j,eax
push eax
push ecx
};
if(str[i]==pipei[j])
{
count[j]+=1;
}
//内循环end
__asm{
pop ecx
pop eax
add eax,1
loop loop2
};
//外循环end
_asm{
pop ecx
pop eax
add eax,1
loop loop1
};
//输出统计个数
//外层循环start
_asm{
mov eax,0 //i=0
mov ecx,26 //i<26
loop3:
mov j,eax
push eax
push ecx
};
if(count[j]>0)
printf("%c=%d\n",pipei[j],count[j]);
//外循环end
_asm{
pop ecx
pop eax
add eax,1
loop loop3
};
}后面有时间再优化了。。。。
优化如下：
需要掌握的知识 if语句的汇编表示
构造单循环：
#include<stdio.h>
void main(){
char str[1024];
char pipei[] = "abcdefghijklmnopqrstuvwxyz";
int count[26]={0};
int i=0,j=0;
char *str1 = "i=%d\n";
char *str2 = "%d=%c\t";
scanf("%s",str);
printf("%s\n",str);
printf(str2,i,str[i]);
//mov edx,dword ptr [ebp-48Ch]
//movsx eax,byte ptr [ebp+edx-400h]
//push eax
//mov ecx,dword ptr [ebp-48Ch]
//push ecx
//mov edx,dword ptr [ebp-498h]
//push edx
//call printf (0040d6c0)
//add esp,0Ch
// ==
//mov edx, i
//movsx eax,str[edx]
//push eax
//mov ecx,i
//push ecx
//mov edx,str2
//push edx
//call printf
//add esp,12 //12=3个变量*4
_asm{
mov i,0 //i=0
start_1024: nop
mov eax,i
add eax,1
mov i,eax //i++
cmp i,10 // if i<10
jge end_1024
//逐个输出 printf(str2,str[i]);
mov edx, i
movsx eax,str[edx]
push eax
mov ecx,i
push ecx
mov edx,str2
push edx
call printf
add esp,12 //12=3个变量*4
jmp start_1024 //for 1024
end_1024: nop
}
}
进一步构造嵌套循环：
#include<stdio.h>
void main(){
char str[1024];
char pipei[] = "abcdefghijklmnopqrstuvwxyz";
int count[26]={0};
int i=0,j=0;
char *str1 = "i=%d\n";
char *str2 = "\n第一层循环%d=%c\n";
char *str3 = "%d=%c\t";
scanf("%s",str);
printf("%s\n",str);
printf(str2,i,str[i]);
_asm{
//第一个外循环
mov i,0 //i=0
start_1024: nop
mov eax,i
add eax,1
mov i,eax //i++
cmp i,10 // if i<10
jge end_1024
//第二个内循环
mov j,0 //j=0
start_26: nop
mov eax,j
add eax,1
mov j,eax //j++
cmp j,26
jge end_26
//逐个输出pipei
mov edx, j
movsx eax,pipei[edx]
push eax
mov ecx,j
push ecx
mov edx,str3
push edx
call printf
add esp,12 //12=3个变量*4
jmp start_26 //for 1024
end_26: nop
//逐个输出 printf(str2,str[i]);
mov edx, i
movsx eax,str[edx]
push eax
mov ecx,i
push ecx
mov edx,str2
push edx
call printf
add esp,12 //12=3个变量*4
jmp start_1024 //for 1024
end_1024: nop
}
}
加入判断与统计输出代码：
#include<stdio.h>
void main(){
char str[1024];
char pipei[] = "abcdefghijklmnopqrstuvwxyz";
int count[26]={0};
int i=0,j=0;
char *str1 = "i=%d\n";
char *str2 = "\n第一层循环%d=%c\n";
char *str3 = "i=%d,j=%d,c=%c\t";
char *str4 = "%c=%d\t";
scanf("%s",str);
printf("%s\n",str);
_asm{
//第一个外循环
mov i,-1 //i=0
start_1024: nop
mov eax,i
add eax,1
mov i,eax //i++
cmp i,1024 // if i<1024
jge end_1024
//判断第i个字符串是否为结束符，如果是则退出总循环
movsx eax,str[eax]
cmp eax,0h
je end_1024
// \n第一层循环%d=%c\n printf(str2,i,str[i]);
mov edx, i
movsx eax,str[edx]
push eax
mov ecx,i
push ecx
mov edx,str2
push edx
call printf
add esp,12 //12=3个变量*4
//第二个内循环
mov j,-1 //j=-1
start_26: nop
mov eax,j
add eax,1
mov j,eax //j++
cmp j,26
jge end_26
//逐个输出 "i=%d,j=%d,c=%c\t"; pipei
mov edx, j
movsx eax,pipei[edx]
push eax
mov ecx,j
push ecx
mov ecx,i
push ecx
mov edx,str3
push edx
call printf
add esp,16 //12=4个变量*4
//判断str[i]是否与pipei[j]相等，相等加一并退出第二循环
//if(str[i]==pipei[j])
mov edx,i
movsx eax,str[edx]
mov ecx,j
movsx edx,pipei[ecx]
cmp eax,edx
jne end_count//不相等
//{count[j]+=1 //相等
mov eax,j
mov ecx,count[eax*4]
add ecx,1
mov edx,j
mov count[edx*4],ecx
//break;
jmp start_1024 //如果找到一个匹配的，则退出第二循环
end_count: nop
jmp start_26 //for 26
end_26: nop
jmp start_1024 //for 1024
end_1024: nop
//到这里统计算法已经结束
//输出统计个数
mov j,-1 //j=-1
start_all: nop
mov eax,j
add eax,1
mov j,eax //j++
cmp j,26
jge end_all
//逐个输出printf(str4,pipei[j],count[j]);
mov edx,j
mov ecx,count[edx*4]
push ecx
movsx eax,pipei[edx]
push eax
mov edx,str4
push edx
call printf
add esp,12 //12=3个变量*4
jmp start_all //for 26
end_all: nop
}
}
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原始发表：2020-02-02 ，如有侵权请联系 cloudcommunity@tencent.com 删除
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