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;
}