贪心算法

例题

1、股票买卖

题目信息

思路

相邻两天，后>前，则交易一次

题解

#include 
#define endl '\n'
#define int long long
#define maxsize 100010
using namespace std;

int n;
int money[maxsize];

signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n;
    int sum=0;
    for(int i=0;i<n;i++)
    {
        cin>>money[i];
    }
    for(int i=0;i<n-1;i++)
    {
        int cha=money[i+1]-money[i];
        if(cha >0)
        {
            sum+=cha;
        }
    }
    cout<<sum<<endl;
    return 0;
}
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2、货仓选址

题目信息

思路

题解

#include 
#define int long long 
#define int long long 
#define maxsize 100010
using namespace std;

int n;
int num[maxsize];

signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n;
    for(int i=0;i<n;i++)
    {
        cin>>num[i];
    }
    sort(num,num+n);
    int c=num[(n-1)/2];
    int sum=0;
    for(int i=0;i<n;i++)
    {
        sum +=abs(num[i]-c);
    }
    cout<<sum<<endl;
    return 0;
}
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3、糖果传递

题目信息

思路

题解

#include 
#define int long long
#define endl '\n'
#define maxsize 1000100
using namespace std;

int n;
int average;
int a[maxsize],c[maxsize];

signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int sum=0;
    int count=0;
    cin>>n;
    for(int i=1;i<=n;i++) cin>>a[i];
    for(int i=1;i<=n;i++) sum+=a[i];
    average=sum/n;
    for(int i=1;i<=n;i++)
    {
        c[i]=c[i-1]+average-a[i];
    }
    sort(c+1,c+n+1);
    int xn=c[(1+n)/2];
    for(int i=1;i<=n;i++) count +=abs(c[i]-xn);
    cout<<count<<endl;
    return 0;
}
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4、雷达设备

题目信息

思路

题解

#include 
#define int long long
#define maxsize 1010
#define endl '\n'
using namespace std;

struct node
{
    double l;
    double r;
}qujian[maxsize];

bool judge(node a,node b)
{
    return a.r<b.r;
}

int n,d;

signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int x,y;
    int count=0;
    bool fail=false;
    cin>>n>>d;
    for(int i=0;i<n;i++)
    {
        cin>>x>>y;
        if(d<y) fail=true;
        else{
            double len=sqrt(d*d-y*y);
            qujian[i].l=x-len;
            qujian[i].r=x+len;
        }
    }
    if(fail) cout<<"-1"<<endl;
    else{
        sort(qujian,qujian+n,judge);
        double jilu=qujian[0].r;
        count=1;
        for(int i=1;i<n;i++)
        {
            if(jilu<qujian[i].l)
            {
                count++;
                jilu=qujian[i].r;
            }
        }
        cout<<count<<endl;
    }
    return 0;
}
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