UVA 673 (13.08.17)

Parentheses Balance

You are given a string consisting of parentheses () and []. Astring of this type is said to be
correct:

(a)if it is the empty string(b)if A and B are correct, AB is correct,(c)if A is correct, (A) and [A] is correct.Write a program that takes a sequence of strings of this type and checktheir correctness. Your program can assume that the maximum stringlength is 128.

Input 

The file contains a positive integer n and a sequence of n strings ofparentheses
() and [], one string a line.

Output 

A sequence of Yes or No on the output file.

Sample Input 

3
([])
(([()])))
([()[]()])()

Sample Output 

Yes
No
Yes

题意: 匹配小括号和中括号~

做法及其注意点:

一种情况是遇到 '(' 或 '[', 那么直接放到栈里不解释~

另一种情况是遇到 ')' 或 ']', 进行判定, 是否前一个是 '(' 或 '[' (注意了, 此时栈也许是空的), 若是, 弹出栈~

最后判断是否为空~

AC代码:

#include<stdio.h>
#include<stack>

using namespace std;

int main() {
int T;
char ch;
scanf("%d", &T);
getchar();
while(T--) {
stack <char> sta;

while(scanf("%c", &ch)) {
if(ch == '\n')
break;
if(sta.empty()) {
sta.push(ch);
continue;
}
if(ch == '(')
sta.push(ch);

if(ch == ')') {
if(sta.top() == '(')
sta.pop();
else
sta.push(ch);
}
if(ch == '[')
sta.push(ch);

if(ch == ']') {
if(sta.top() == '[')
sta.pop();
else
sta.push(ch);
}
}

if(sta.empty())
printf("Yes\n");
else
printf("No\n");
}
return 0;
}