删除c语言中的所有注释语句



原文链接：http://lixing123.com/archives/310

学习《C程序设计语言》到第1章最后，有一道题目：

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1. 编写一个删除C语言程序中所有的注释语句。要正确处理带引号的字符串与字符常量。在C语言中,注释不允许嵌套。  

下面把代码贴出来：

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1. #include <stdio.h>  
2.   
3. int state;  
4.   
5. int c1,c2;  
6.   
7. void change_state(int c);  
8.   
9. int main(int argc, const char * argv[]) {  
10.     int c;  
11.     state = 0;  
12.     c1 = 0;  
13.     c2 = 0;  
14.     while ((c=getchar())!=EOF) {  
15.         c1 = c2;  
16.         c2 = c;  
17.         change_state(c);  
18.     }  
19.     if (/* DISABLES CODE */ (0)==1) {  
20.         printf("just test://abcd");  
21.         printf("just test:/*hello*/");  
22.     }  
23. }  
24.   
25. /*状态机函数*/  
26. void change_state(int c){  
27.     if (state==0) {//普通状态  
28.         if (c=='/') {  
29.             state = 1;  
30.         }else if (c=='"'){  
31.             state = 5;  
32.             putchar(c);  
33.         }else if (c=='\''){  
34.             state = 6;  
35.             putchar(c);  
36.         }  
37.         else{  
38.             state = 0;  
39.             putchar(c);  
40.         }  
41.     }else if (state==1) {//检测到1个'/'  
42.         if (c=='/') {  
43.             state = 2;  
44.         }else if (c=='*'){  
45.             state = 3;  
46.         }else{  
47.             state = 0;  
48.             putchar(c1);  
49.             putchar(c);  
50.         }  
51.     }else if (state==2) {// "//"注释状态  
52.         if (c=='\n') {  
53.             state = 0;  
54.             putchar(c);  
55.         }else{  
56.             state = 2;  
57.         }  
58.     }else if (state==3) {// "/*"注释状态  
59.         if (c=='*') {  
60.             state = 4;  
61.         }else{  
62.             state = 3;  
63.         }  
64.     }else if (state==4) {  
65.         if (c=='/') {  
66.             state = 0;  
67.         }else{  
68.             state = 3;  
69.         }  
70.     }else if (state==5){//在"字符串里  
71.         if (c=='"') {  
72.             state = 0;  
73.             putchar(c);  
74.         }else if(c=='\\'){  
75.             state = 7;  
76.             putchar(c);  
77.         }else{  
78.             state = 5;  
79.             putchar(c);  
80.         }  
81.     }else if (state==6){//在'字符里  
82.         if (c=='\'') {  
83.             state = 0;  
84.             putchar(c);  
85.         }else if(c=='\\'){  
86.             state = 8;  
87.             putchar(c);  
88.         }else{  
89.             state = 6;  
90.             putchar(c);  
91.         }  
92.     }else if (state==7){//在"字符串里的"\"  
93.         state = 5;  
94.         putchar(c);  
95.     }else if (state==8){//在'字符串里的"\"  
96.         state = 6;  
97.         putchar(c);  
98.     }  
99. }  

#include <stdio.h>int state;int c1,c2;void change_state(int c);int main(int argc, const char * argv[]) {    int c;    state = 0;    c1 = 0;    c2 = 0;    while ((c=getchar())!=EOF) {        c1 = c2;        c2 = c;        change_state(c);    }    if (/* DISABLES CODE */ (0)==1) {        printf("just test://abcd");        printf("just test:/*hello*/");    }}/*状态机函数*/void change_state(int c){    if (state==0) {//普通状态        if (c=='/') {            state = 1;        }else if (c=='"'){            state = 5;            putchar(c);        }else if (c=='\''){            state = 6;            putchar(c);        }        else{            state = 0;            putchar(c);        }    }else if (state==1) {//检测到1个'/'        if (c=='/') {            state = 2;        }else if (c=='*'){            state = 3;        }else{            state = 0;            putchar(c1);            putchar(c);        }    }else if (state==2) {// "//"注释状态        if (c=='\n') {            state = 0;            putchar(c);        }else{            state = 2;        }    }else if (state==3) {// "/*"注释状态        if (c=='*') {            state = 4;        }else{            state = 3;        }    }else if (state==4) {        if (c=='/') {            state = 0;        }else{            state = 3;        }    }else if (state==5){//在"字符串里        if (c=='"') {            state = 0;            putchar(c);        }else if(c=='\\'){            state = 7;            putchar(c);        }else{            state = 5;            putchar(c);        }    }else if (state==6){//在'字符里        if (c=='\'') {            state = 0;            putchar(c);        }else if(c=='\\'){            state = 8;            putchar(c);        }else{            state = 6;            putchar(c);        }    }else if (state==7){//在"字符串里的"\"        state = 5;        putchar(c);    }else if (state==8){//在'字符串里的"\"        state = 6;        putchar(c);    }}

以本段代码作为输入，结果如下：

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1. #include <stdio.h>  
2.   
3. int state;  
4.   
5. int c1,c2;  
6.   
7. void change_state(int c);  
8.   
9. int main(int argc, const char * argv[]) {  
10.     int c;  
11.     state = 0;  
12.     c1 = 0;  
13.     c2 = 0;  
14.     while ((c=getchar())!=EOF) {  
15.         c1 = c2;  
16.         c2 = c;  
17.         change_state(c);  
18.     }  
19.     if ( (0)==1) {  
20.         printf("just test://abcd");  
21.         printf("just test:/*hello*/");  
22.     }  
23. }  
24.   
25.   
26. void change_state(int c){  
27.     if (state==0) {  
28.         if (c=='/') {  
29.             state = 1;  
30.         }else if (c=='"'){  
31.             state = 5;  
32.             putchar(c);  
33.         }else if (c=='\''){  
34.             state = 6;  
35.             putchar(c);  
36.         }  
37.         else{  
38.             state = 0;  
39.             putchar(c);  
40.         }  
41.     }else if (state==1) {  
42.         if (c=='/') {  
43.             state = 2;  
44.         }else if (c=='*'){  
45.             state = 3;  
46.         }else{  
47.             state = 0;  
48.             putchar(c1);  
49.             putchar(c);  
50.         }  
51.     }else if (state==2) {  
52.         if (c=='\n') {  
53.             state = 0;  
54.             putchar(c);  
55.         }else{  
56.             state = 2;  
57.         }  
58.     }else if (state==3) {  
59.         if (c=='*') {  
60.             state = 4;  
61.         }else{  
62.             state = 3;  
63.         }  
64.     }else if (state==4) {  
65.         if (c=='/') {  
66.             state = 0;  
67.         }else{  
68.             state = 3;  
69.         }  
70.     }else if (state==5){  
71.         if (c=='"') {  
72.             state = 0;  
73.             putchar(c);  
74.         }else if(c=='\\'){  
75.             state = 7;  
76.             putchar(c);  
77.         }else{  
78.             state = 5;  
79.             putchar(c);  
80.         }  
81.     }else if (state==6){  
82.         if (c=='\'') {  
83.             state = 0;  
84.             putchar(c);  
85.         }else if(c=='\\'){  
86.             state = 8;  
87.             putchar(c);  
88.         }else{  
89.             state = 6;  
90.             putchar(c);  
91.         }  
92.     }else if (state==7){  
93.         state = 5;  
94.         putchar(c);  
95.     }else if (state==8){  
96.         state = 6;  
97.         putchar(c);  
98.     }  

#include <stdio.h>int state;int c1,c2;void change_state(int c);int main(int argc, const char * argv[]) {    int c;    state = 0;    c1 = 0;    c2 = 0;    while ((c=getchar())!=EOF) {        c1 = c2;        c2 = c;        change_state(c);    }    if ( (0)==1) {        printf("just test://abcd");        printf("just test:/*hello*/");    }}void change_state(int c){    if (state==0) {        if (c=='/') {            state = 1;        }else if (c=='"'){            state = 5;            putchar(c);        }else if (c=='\''){            state = 6;            putchar(c);        }        else{            state = 0;            putchar(c);        }    }else if (state==1) {        if (c=='/') {            state = 2;        }else if (c=='*'){            state = 3;        }else{            state = 0;            putchar(c1);            putchar(c);        }    }else if (state==2) {        if (c=='\n') {            state = 0;            putchar(c);        }else{            state = 2;        }    }else if (state==3) {        if (c=='*') {            state = 4;        }else{            state = 3;        }    }else if (state==4) {        if (c=='/') {            state = 0;        }else{            state = 3;        }    }else if (state==5){        if (c=='"') {            state = 0;            putchar(c);        }else if(c=='\\'){            state = 7;            putchar(c);        }else{            state = 5;            putchar(c);        }    }else if (state==6){        if (c=='\'') {            state = 0;            putchar(c);        }else if(c=='\\'){            state = 8;            putchar(c);        }else{            state = 6;            putchar(c);        }    }else if (state==7){        state = 5;        putchar(c);    }else if (state==8){        state = 6;        putchar(c);    }

perfect！

感谢@roma823 及其文章：http://blog.csdn.net/roma823/article/details/6364849