题目地址:http://pat.zju.edu.cn/contests/pat-a-practise/1057
用树状数组和二分搜索解决，对于这种对时间复杂度要求高的题目，用C的输入输出显然更好
#include <cstdio>
#include <string>
#include <vector>
#include <stack>
using namespace std;const int NUM=100001;
struct TreeArray
{
vector<int> cStore;
TreeArray()
{
cStore=vector<int>(NUM,0);
}
int lowerBit(int x)
{
return x&(-x);
}
void add(int location,int addedValue)
{
while(location<=NUM)
{
cStore[location]+=addedValue;
location+=lowerBit(location);
}
}
int getSum(int location)
{
int sum(0);
while(location>0)
{
sum+=cStore[location];
location-=lowerBit(location);
}
return sum;
}int findMedian(int toFind,int low=1,int high=NUM)
{
if(low==high)
return low;
int median=(low+high)>>1;
if(getSum(median)<toFind)
{
return findMedian(toFind,median+1,high);
}
else
{
return findMedian(toFind,low,median);
}
}
};TreeArray treeArray;
stack<int> s;int _tmain(int argc, _TCHAR* argv[])
{
int N;
scanf("%d",&N);
char command[20];
int key;
for(int i=0;i<N;++i)
{
scanf("%s",command);
switch(command[1])
{
case ‘u‘:
scanf("%d",&key);
s.push(key);
treeArray.add(key,1);
break;
case ‘e‘:
if(s.empty())
printf("Invalid\n");
else
{
printf("%d\n",treeArray.findMedian((s.size()+1)/2));
}
break;
case ‘o‘:
if(s.empty())
printf("Invalid\n");
else
{
key=s.top();
s.pop();
printf("%d\n",key);
treeArray.add(key,-1);
break;
}
}
}
return 0;
}
PAT 1057. Stack (30)