栈的应用实践——括号匹配的检验

目的：检验一个字符串中的大括号，中括号，小括号是否匹配。

方法：数据结构c语言版提出的期待的急迫程度描述这个问题，具体的思路为：

处于栈顶的括号总是最急迫的期待着和下一个读入的括号进行匹配

如果下一个括号可以匹配，那么栈顶括号出栈，之后新的栈顶处于最急迫的地位，或者空栈继续读入；

如果下一个括号不可以匹配栈顶，则这个括号进栈并成为新的栈顶，成为最急迫的元素，原先的急迫度则降了一级。

可以预知的是，若是字符串中括号最终可以匹配，读取所有字符后，栈将为空，可以以此作为判断的最终条件。

写的不规范之处，还请指出，见谅。

//Main idea
//Pushing a bracket A into a stack,
//if the bracket A cannot match the bracket B in top of the stack
//However,if they can match each other,not only A cannot pushed into stack
//but B will be popped from the stack.

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
typedef struct Node
{
char bracket;
struct Node *next;
}StackNode; //define the Node of stack

int emptystack(StackNode *);//Judge if it is a empty or not
StackNode *push(StackNode *,char);//push a character in stack
StackNode *pop(StackNode *);//pop the character that is in top
StackNode *creatstack();//initalize a stack
int judgecharacter(char);//judge if a character is a bracket or not
int judgematching(char,char);//judge if two bracket can match each other or not

int main(int argc,char *argv[])
{
if (argc!=2)
{
printf("True Usage:bracket String\n");
exit(0);
}
//Make sure that there are two command line parameters
StackNode *s=creatstack();//get a empty stack
int i;
for(i=0;i<strlen(argv[1]);i++)//string traversal
{
if(judgecharacter(argv[1][i]))//find bracket
{
//first bracket in stack,but if the string don't include any bracket,
//the final outcome is that brackets are matched
if(emptystack(s))
s=push(s,argv[1][i]);
else
{
if(judgematching(s->bracket,argv[1][i]))
s=pop(s);
else
s=push(s,argv[1][i]);
}
}
}
if(emptystack(s))
printf("Brackets are matched in this string\n");
else
printf("Brackets are not matched\n");
return 0;
}

int emptystack(StackNode *s)
{
if(s->next==NULL)
return 1;
else
return 0;
}

StackNode *push(StackNode *s,char e)
{
StackNode *new=(StackNode *)malloc(sizeof(StackNode));
new->next=s;
new->bracket=e;
return new;
}

StackNode *pop(StackNode *s)
//In main function,we have considered that stack is empty
//so ,now we can ignore this case
{
StackNode *temp=s->next;
free(s);
return temp;
}

StackNode *creatstack()
//creat a empty stack which include one node
{
StackNode *s=(StackNode *)malloc(sizeof(StackNode));
s->next=NULL;
return s;
}

int judgecharacter(char h)
{
if(h=='['||h==']'||h=='{'||h=='}'||h=='('||h==')')
return 1;
else
return 0;
}

int judgematching(char w,char f)
//please notice that position is different between w and f
{
if((w=='{'&&f=='}')||(w=='['&&f==']')||(w=='('&&f==')'))
return 1;
else
return 0;

}

用法应该在终端下，给予命令行参数。自己测试的第二个参数字符串需要用双引号括起。