数据结构07——表达式括号匹配

假设一个括号表达式可以包含3种括号：（），{}，[],它们可按任意次序嵌套，编写判断表达式中括号是否正确匹配的程序。

若正确匹配输出yes,否则输出no。

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

typedef struct  stack{
	struct stack *top;
	struct stack *bottom;
	struct stack *next;
	char sign;
}stack;

void init(stack *list){
	list->bottom=(stack*)malloc(sizeof(stack));
	list->bottom->next==NULL;
	list->top=list->bottom;
}

void push(stack *list,char s){
	stack *p;
	p=(stack*)malloc(sizeof(stack));
	p->sign=s;
	p->next=list->top;
	list->top=p;
}

void pop(stack *list){
	stack *p;
	p=list->top;
	list->top=list->top->next;
	free(p);
}

int main(){
	char a[100];
	int i;
	stack *list;
	list=(stack*)malloc(sizeof(stack));
	init(list);
	scanf("%s",&a);
	for(i=0;i<strlen(a);i++){
		if(a[i]=='{'||a[i]=='('||a[i]=='['){
			push(list,a[i]);
		}
		else if(a[i]=='}'){
			if(list->top->sign=='{'){
				pop(list);
			}
			else{
				printf("no\n");
				return 0;
			}
		}
		else if(a[i]==')'){
			if(list->top->sign=='('){
				pop(list);
			}
			else{
				printf("no\n");
				return 0;
			}
		}
		else if(a[i]==']'){
			if(list->top->sign=='['){
				pop(list);
			}
			else{
				printf("no\n");
				return 0;
			}
		}
	}
	if(list->top == list->bottom){
		printf("yes\n");
		return 0;
	}
}