A	Sumo and Keyboard-Cat

水题，但是总要wa一次。第一次用string写题目，wa了一发，不知道是为什么，到现在还是没有搞清楚，后来用char数组就过了，奇怪奇怪真奇怪

wa代码：

#include<iostream>
#include<string>
#include<string.h>
using namespace std;
typedef long long ll;
int main()
{
    ll i,s=0;
    string str;
    cin>>str;
    for(i=0;i<str.length()-1;i++)
    {
        if(i==0)
        {
            if(str[1]>='a'&&str[1]<='z')
            {
                s++;
            }
        }
        else
        {
            if(str[i]>='A'&&str[i]<='Z'&&str[i+1]>='a'&&str[i+1]<='z')
                s++;
            if(str[i+1]>='A'&&str[i+1]<='Z'&&str[i]>='a'&&str[i]<='z')
                s++;
        }
    }
    cout<<s<<endl;
}

char数组代码：

#include<iostream>
#include<string>
#include<string.h>
using namespace std;
typedef long long ll;
int main()
{
    ll i,s=0;
    string str;
    cin>>str;
    for(i=0;i<str.length()-1;i++)
    {
        if(i==0)
        {
            if(str[1]>='a'&&str[1]<='z')
            {
                s++;
            }
        }
        else
        {
            if(str[i]>='A'&&str[i]<='Z'&&str[i+1]>='a'&&str[i+1]<='z')
                s++;
            if(str[i+1]>='A'&&str[i+1]<='Z'&&str[i]>='a'&&str[i]<='z')
                s++;
        }
    }
    cout<<s<<endl;
}

B	Sumo and His Followers

先sort一边然后再用前缀和即可

#include<iostream>
#include<string.h>
#include<algorithm>
typedef long long ll;
using namespace std;
int main()
{
    ll repeat,i;
    cin>>repeat;
    while(repeat--)
    {
        ll n;
        double sum=0;
        cin>>n;
        ll b,a[n];
        double s=0;
        if(n==1)
        {
            cin>>b;
            sum=0.00;
        }
        else
        {
            for(i=0;i<n;i++)
            {
                cin>>a[i];
            }
            sort(a,a+n);
            for(i=1;i<n;i++)
            {
                s+=a[i-1];
                sum+=s;
            }
            sum/=n;
        }
        printf("%.2f\n",sum);
        sum=0;
        s=0;
    }
}

F	Sumo and Luxury Car

规律题+快速幂

n->s
1->1
2->4
3->12
4->32
5->80
...

s=n*2^(n-1)

别忘了1e9+7哟

#include<iostream>
#include<algorithm>
typedef unsigned long long ll;
using namespace std;
ll quickpow(ll x,ll y)
{
    ll mod=1000000007;
    ll n=1;
    n%=mod;
    while(y!=0)
    {
        if (y&1!=0) n=n*x%mod;
        y=y>>1;
        x=x*x%mod;
    }
    n%=mod;
    return n;
}
int main()
{
    ll repeat,i;
    scanf("%lld",&repeat);
    while(repeat--)
    {
        ll a;
        cin>>a;
        ll sum=0;
        sum=a*quickpow(2,a-1);
        sum%=1000000007;
        cout<<sum<<endl;
    }
}

第十七届浙大城市学院程序设计竞赛（同步赛）

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