P1241 括号序列

RE一半

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<stack>

using namespace std;

string s;
char ans[400];
bool vis[400];
int cnt = 0;

stack<pair<int, char>> sta;

bool check(char ch1, char ch2)
{
	return (ch1 == '(' && ch2 == ')') || (ch1 == '[' && ch2 == ']');
}

void print(char a)
{
	if (a == '[' || a == ']')
	{
		cout << "[]";
	}
	if (a == ')' || a == '(')
	{
		cout << "()";
	}
}

int main()
{
	cin >> s;
	for (auto ch : s)
	{
		ans[++cnt] = ch;
		if (ch == '[' || ch == '(')
			sta.push({cnt,ch}); 
		else if (check(sta.top().second, ch))
		{
			vis[cnt] = true;
			vis[sta.top().first] = true;
			sta.pop();
		}
	}
	for (int i = 1; i <= cnt; i++)
	{
		if(!vis[i])
		{
			print(ans[i]);
		}
		else
		{
			cout<<ans[i];
		}
	}
	return 0;
}

问题在于有时候可能栈是空的，这时再执行调取栈顶和出栈等操作就会导致运行时错误。

特判即可。

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<stack>

using namespace std;

string s;
char ans[400];
bool vis[400];
int cnt = 0;

stack<pair<int, char>> sta;

bool check(char ch1, char ch2)
{
	return (ch1 == '(' && ch2 == ')') || (ch1 == '[' && ch2 == ']');
}

void print(char a)
{
	if (a == '[' || a == ']')
	{
		cout << "[]";
	}
	if (a == ')' || a == '(')
	{
		cout << "()";
	}
}

int main()
{
	cin >> s;
	for (auto ch : s)
	{
		ans[++cnt] = ch;
		if (ch == '[' || ch == '(')
		{
			sta.push({cnt,ch}); 
			continue;
		}
		if (sta.empty())
		{
			continue;
		}
		if (check(sta.top().second, ch))
		{
			vis[cnt] = true;
			vis[sta.top().first] = true;
			sta.pop();
		}
	}
	for (int i = 1; i <= cnt; i++)
	{
		if(!vis[i])
		{
			print(ans[i]);
		}
		else
		{
			cout<<ans[i];
		}
	}
	return 0;
}