HDU 5349 MZL's simple problem（队列）

题目地址：点击打开链接

思路：刚开始还以为每次输出最大值还要删除呢，调了半天没有过，看别人的代码，没看到把最大值弹出，每次只保留最大值，以为是数据的BUG，结果又一看题query的意思是查询.。。。把自己的代码改了一下，没过，直接参考写了个用优先队列和队列写的代码，有时间改一下，还有就是注意有多组测试数据，看到有人用multiset也A了，有时间学一下

错误代码1：

#include <iostream>
#include <queue>
#include <cstdio>

using namespace std;

struct num
{
int x;
bool operator < (const num &a) const
{
return x < a.x;//最大值优先
}
};

int main()
{
priority_queue<num> pq;
num out,in;
int n,a,b,sum;
while(scanf("%d",&n) != EOF)
{
sum = 0;
while(n--)
{
while(!pq.empty())
pq.pop();
scanf("%d",&a);
if(a == 1)
{
scanf("%d",&b);
in.x = b;
pq.push(in);
}
else if(a == 2)
{
if(!pq.empty())
sum++;
else
sum = 0;
}
else
{
if(sum < pq.size() && !pq.empty())
{
out = pq.top();
pq.pop();
printf("%d\n",out.x);
}
else
{
printf("0\n");
}
}
}
}
return 0;
}

错误代码2：

#include <iostream>
#include <queue>
#include <cstdio>

using namespace std;

struct num
{
int x;
bool operator < (const num &a) const
{
return x < a.x;//最大值优先
}
};

int main()
{
priority_queue<num> pq;
num out,in;
int n,a,b,sum;
while(scanf("%d",&n) != EOF)
{
sum = 0;
while(n--)
{
while(!pq.empty())
pq.pop();
scanf("%d",&a);
if(a == 1)
{
scanf("%d",&b);
in.x = b;
pq.push(in);
}
else if(a == 2)
{
if(!pq.empty())
sum++;
}
else
{
if(sum < pq.size())
{
out = pq.top();
printf("%d\n",out.x);
}
else
{
printf("0\n");
}
}
}
}
return 0;
}

AC代码：

#include <iostream>
#include <queue>
#include <cstdio>

using namespace std;

const int inf = 0x3f3f3f3f;

int main()
{
int n,a,b,max1;
while(scanf("%d",&n) != EOF)
{
queue<int> q;//在里面定义省得清空
max1 = -inf;
while(n--)
{
scanf("%d",&a);
if(a == 1)
{
scanf("%d",&b);
q.push(b);
max1 = max(max1,b);
}
else if(a == 2)
{
if(!q.empty())
{
q.pop();
}
if(q.empty())
max1  = -inf;
}
else
{
if(q.empty())
{
printf("0\n");
}
else
{
printf("%d\n",max1);
}
}
}
}
return 0;
}

AC代码：

#include <iostream>
#include <queue>
#include <cstdio>

using namespace std;

const int inf = 0x3f3f3f3f;

struct num//不用重新定义，因为默认排序是升序，
{
int x;
bool operator < (const num &a) const
{
return x < a.x;//最大值优先
}
};

int main()
{
num in;
int n,a,b,max1;
while(scanf("%d",&n) != EOF)
{
priority_queue<num> pq;//在里面定义省得清空
max1 = -inf;
while(n--)
{
scanf("%d",&a);
if(a == 1)
{
scanf("%d",&b);
in.x = b;
pq.push(in);
max1 = max(max1,b);
}
else if(a == 2)
{
/*if(!pq.empty())
{
pq.pop();不能这样搞，会导致队列没值，最大值没变
}
else
max1  = -inf;*/
if(!pq.empty())
{
pq.pop();
}
if(pq.empty())
max1  = -inf;
}
else
{
if(pq.empty())
{
printf("0\n");
}
else
{
printf("%d\n",max1);
}
}
}
}
return 0;
}

大神地址：点击打开链接