ZJU-PAT 1057. Stack (30) 浙大2013年上机复试第三题

#pragma warning (disable:4786)
#include<iostream>
#include<string>
#include<cstdio>
#include<algorithm>
#include<map>
using namespace std;

int n,d;;
int A[10005],B[10005];

int select(int num)
{
	for(int i=1;i<=d;i++) B[i]=A[i];
	sort(B+1,B+d+1);
	return B[num];
}

void process()
{
	char operate[1000];
	scanf("%s",operate);
	string s=operate;

	if(s=="Pop")
	{
		if(d==0)
			printf("Invalid\n");
		else 
		{
			printf("%d\n",A[d]);
			d--;
		}
	}
	else if(s=="PeekMedian")
	{
		if(d==0)
			printf("Invalid\n");
		else
		{
			int num;
			if(d%2==0) num=d/2;
			else
				num=(d+1)/2;
			printf("%d\n",select(num));
		}
	}
	else if(s=="Push")
	{
		int b;
		scanf("%d",&b);
		A[++d]=b;
	}
}

int main()
{
	//freopen("1.txt","r",stdin);
	while(scanf("%d",&n)!=EOF)
	{
		d=0;
		for(int i=0;i<n;i++) 
			process();
	}
	return 0;
}

利用树状数组+二分查找进行定位

#pragma warning (disable:4786)
#include<iostream>
#include<string>
#include<cstdio>
#include<algorithm>
#include<map>
using namespace std;

const int N=100005;

int n,d;
int A[N],C[N];

int lowbit(int x)
{
    return x&(-x);
}

void update(int x,int num)
{
    while(x<=N)
    {
        C[x]+=num;
        x+=lowbit(x);
    }
}

int getsum(int x)
{
    int sum=0;
    while(x>0)
    {
        sum+=C[x];
        x-=lowbit(x);
    }
    return sum;
}

int select(int num)
{
    int L=0,R=N-1,M,ans;

    while(L<R-1)
    {
        M=(L+R)/2;
        ans=getsum(M);

        if(ans<num) L=M;
        else
            R=M;
    }
    return R;
}

void process()
{
    char operate[1000];
    scanf("%s",operate);
    string s=operate;

    if(s=="Pop")
    {
        if(d==0)
            printf("Invalid\n");
        else
        {
            printf("%d\n",A[d]);
            update(A[d],-1);
            d--;
        }
    }
    else if(s=="PeekMedian")
    {
        if(d==0)
            printf("Invalid\n");
        else
        {
            int num;
            if(d%2==0) num=d/2;
            else
                num=(d+1)/2;
            printf("%d\n",select(num));
        }
    }
    else if(s=="Push")
    {
        int b;
        scanf("%d",&b);
        update(b,1);
        A[++d]=b;
    }
}

int main()
{
    while(scanf("%d",&n)!=EOF)
    {
        d=0;
        for(int i=0; i<10005; i++) C[i]=0;
        for(int i=0; i<n; i++)
            process();
    }
    return 0;
}