算法笔记--树状数组

Posted 2020-10-12 Wisdom+.+

区间和模板：

const int N=1e5+5;
int c[N];
int n;
int lowbit(int x)
{
    return x&(-x);
}
int sum(int x)
{
    int ret=0;
    while(x)
    {
        ret+=c[x];
        x-=lowbit(x);
    }
    return ret;
}
void update(int x,int d)
{
    while(x<=n)
    {
        c[x]+=d;
        x+=lowbit(x);
    }
}

1.单点更新，区间求和

HDU - 1166

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define mem(a,b) memset(a,b,sizeof(a))

const int N=1e5+5;
int c[N];
int n;
int lowbit(int x)
{
    return x&(-x);
}
int sum(int x)
{
    int ret=0;
    while(x)
    {
        ret+=c[x];
        x-=lowbit(x);
    }
    return ret;
}
void update(int x,int d)
{
    while(x<=n)
    {
        c[x]+=d;
        x+=lowbit(x);
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int T,a,l,r;
    int cnt=0;
    string s;
    cin>>T;
    while(T--)
    {
        cin>>n;
        mem(c,0); 
        for(int i=1;i<=n;i++)cin>>a,update(i,a);
        cout<<"Case "<<++cnt<<":"<<endl;
        while(cin>>s)
        {
            if(s=="End")break;
            if(s=="Query")
            {
                cin>>l>>r;
                cout<<sum(r)-sum(l-1)<<endl;
            }
            else if(s=="Add")
            {
                cin>>l>>r;
                update(l,r);
            }
            else if(s=="Sub")
            {
                cin>>l>>r;
                update(l,-r);
            }
        } 
    }
    return 0;
}

View Code

2.区间更新，单点求值

HDU - 1556

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define mem(a,b) memset(a,b,sizeof(a))

const int N=1e5+5;
int c[N];
int n;
int lowbit(int x)
{
    return x&(-x);
}
int sum(int x)
{
    int ret=0;
    while(x)
    {
        ret+=c[x];
        x-=lowbit(x);
    }
    return ret;
}
void update(int x,int d)
{
    while(x<=n)
    {
        c[x]+=d;
        x+=lowbit(x);
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int l,r;
    while(cin>>n)
    {
        mem(c,0);
        for(int i=1;i<=n;i++)
        {
            cin>>l>>r;
            update(l,1);
            update(r+1,-1);
        } 
        for(int i=1;i<=n;i++)
        {
            cout<<sum(i);
            if(i!=n)cout<<‘ ‘;
            else cout<<endl;
        } 
    }
    return 0;
}

View Code

参考博客：http://blog.csdn.net/yexiaohhjk/article/details/51077545