Week 5 item 3 - matching parentheses

Tip:
(1) When the left bracket is encountered, the stack will issue a symbol to see if it is matched. If pairing, continue until you have read all the symbols and the stack is empty. If there is a mismatch in the middle, or____ Then we can draw the conclusion that there is no match.  
(2) You can also design a function whose return value is Boolean, whose parameter is the expression to be matched, and whose parameter is a string.

Both solutions have bugs: when the number of parentheses entered is greater on the left than on the right, for example{ }}}}}}}}}, a "match the correct bug" will appear.

Solution 1: for the header file sqstack.h, see[ Sequential stack algorithm library ], using Chain stack You can copy

1. <span style="font-family:SimSun;font-size:12px;">#include <stdio.h>
2. #include "sqstack.h"
3. int main()
4. {
5. char c;
6. char st[50];
7. int d=1, i;
8. SqStack *s;
9. InitStack(s);
10. printf("Please enter an expression:");
11. scanf("%s", st);
12. for(i=0; st[i]!='\0'&&d; i++)
13. {
14. switch(st[i])
15. {
16. case'(':
17. case'[':
18. case'{':
19. Push(s, st[i]);
20. break;
21. case')':
22. Pop(s, c);
23. if(c!='(') d=0;
24. break;
25. case']':
26. Pop(s, c);
27. if(c!='[') d=0;
28. break;
29. case'}':
30. Pop(s,c);
31. if(c!='{') d=0;
32. break;
33. }
34. }
35. if(StackEmpty(s)&&d==1)
36. printf("Correct pairing!!\n");
37. else
38. printf("Pairing error!!\n");
39. return 0;
40. }</span>

1. #include <stdio.h>
2. #include "sqstack.h"
4. bool isMatch(char *st)
5. {
6. int d=1, i;
7. char c;
8. SqStack *s;
9. InitStack(s);
10. for(i=0; st[i]!='\0'&&d; i++)
11. {
12. switch(st[i])
13. {
14. case'(':
15. case'[':
16. case'{':
17. Push(s, st[i]);
18. break;
19. case')':
20. Pop(s, c);
21. if(c!='(') d=0;
22. break;
23. case']':
24. Pop(s, c);
25. if(c!='[') d=0;
26. break;
27. case'}':
28. Pop(s,c);
29. if(c!='{') d=0;
30. break;
31. }
32. }
33. if(StackEmpty(s)&&d==1)
34. return true;
35. else
36. return false;
37. }
39. int main()
40. {
42. char st[50];
43. printf("Please enter an expression:");
44. scanf("%s", st);
45. if(isMatch(st))
46. printf("Correct pairing!!\n");
47. else
48. printf("Pairing error!!\n");
49. return 0;
50. }

31 May 2020, 10:37 | Views: 3571