LeetCode | Valid Parentheses（括号匹配）

Given a string containing just the characters

'('

,

')'

,

'{'

,

'}'

,

'['

and

']'

,
determine if the input string is valid.

The brackets must close in the correct order,

"()"

and

"()[]{}"

are
all valid but

"(]"

and

"([)]"

are
not.

题意很简单，就是判断是否匹配。通过栈来实现，如果左括号等，就入栈，如果右括号类，就出栈并判断是否匹配。当全部匹配完了，还要判断栈是否为空，不为空，也代表匹配不成功！

void ValidParentheses(char *str)
{
if(str == NULL){
printf("empty\n");
return ;
}

char ch;
SqStack S;
int len = strlen(str);
InitStack(&S);
if(len % 2){
printf("odd\n");
return;
}
for(int i = 0;i < len;++i){
if(str[i] == '(' || str[i] == '[' || str[i] == '{'){
Push(&S,str[i]);
}else if(str[i] == ')' || str[i] == ']' || str[i] == '}'){
if(IsEmpty(S)){ //在POP函数中已经设置了错误判断，如果为空，就报错并退出循环。
printf("invalid!\n");   //但是直接退出程序不好，所有就提前判断是否为空，为空就报错，退出函数即可。
return;
}
ch = Pop(&S);
if(!Match(ch,str[i])){
printf("invalid\n");
return ;
}
}else{  //处理输入其他字符的情况
printf("the char doesn't correct!\n");
return ;
}
}
if(!IsEmpty(S)){
printf("doesn't match!\n");
}else
printf("match!\n");
}

完整代码如下：

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

#define STACKSIZEINIT 50
#define INCREMENT 10

typedef struct{
char *base;
char *top;
int stacksize;
}SqStack;

void InitStack(SqStack *S)
{
S->base = (char *)malloc(STACKSIZEINIT * sizeof(char));
if(S->base == NULL){
printf("malloc error\n");
exit(1);
}
S->top = S->base;
S->stacksize = STACKSIZEINIT;
}

void Push(SqStack *S,char ch)
{
if(S->top - S->base >= S->stacksize){
S->base = (char *)realloc(S->base,(S->stacksize + INCREMENT)*sizeof(char));
if(S->base == NULL){
printf("malloc error\n");
exit(1);
}
S->top = S->base + S->stacksize;
S->stacksize += INCREMENT;
}
*(S->top++) = ch;
}

int IsEmpty(SqStack S)
{
return S.base == S.top;
}

char Pop(SqStack *S)
{
char ch;
if(IsEmpty(*S)){
printf("stack empty\n");
exit(1);
}
ch = *(--S->top);
return ch;
}

int Match(char a,char b)
{
switch(a){
case '(':
return b == ')';
case '[':
return b == ']';
case '{':
return b == '}';
default :
return 0;
}
}

void ValidParentheses(char *str)
{
if(str == NULL){
printf("empty\n");
return ;
}

char ch;
SqStack S;
int len = strlen(str);
InitStack(&S);
if(len % 2){
printf("odd\n");
return;
}
for(int i = 0;i < len;++i){
if(str[i] == '(' || str[i] == '[' || str[i] == '{'){
Push(&S,str[i]);
}else if(str[i] == ')' || str[i] == ']' || str[i] == '}'){
if(IsEmpty(S)){ //在POP函数中已经设置了错误判断，如果为空，就报错并退出循环。
printf("invalid!\n");   //但是直接退出程序不好，所有就提前判断是否为空，为空就报错，退出函数即可。
return;
}
ch = Pop(&S);
if(!Match(ch,str[i])){
printf("invalid\n");
return ;
}
}else{  //处理输入其他字符的情况
printf("the char doesn't correct!\n");
return ;
}
}
if(!IsEmpty(S)){
printf("doesn't match!\n");
}else
printf("match!\n");
}

int main()
{
char buf[20];

while(scanf("%s",buf)!=EOF){
ValidParentheses(buf);
}
return 0;
}