线段树模板

Posted 2021-03-24 zenghuan0620

区间修改：

#include<bits/stdc++.h>
using namespace std;

const int N=1e5+5;
int sum[N<<2],lazy[N<<2],a[N];
void pushup(int rt)
{
    sum[rt]=sum[rt<<1]+sum[rt<<1|1];
}
void pushdown(int l,int r,int rt)
{
    if(lazy[rt]==0)return;
    lazy[rt<<1]+=lazy[rt];
    lazy[rt<<1|1]+=lazy[rt];
    int mid=(l+r)>>1;
    sum[rt<<1]+=(mid-l+1)*lazy[rt];
    sum[rt<<1|1]+=(r-mid)*lazy[rt];
    lazy[rt]=0;
}
void build(int l,int r,int rt)
{
    lazy[rt]=0;
    if(l==r)
    {
        sum[rt]=a[l];
        return;
    }
    int mid=(l+r)>>1;
    pushdown(l,r,rt);
    build(l,mid,rt<<1);
    build(mid+1,r,rt<<1|1);
    pushup(rt);
}
void update(int L,int R,int val,int l,int r,int rt)
{
    if(L<=l&&r<=R)
    {
        lazy[rt]+=val;
        sum[rt]+=(r-l+1)*val;
        return;
    }
    int mid=(l+r)>>1;
    pushdown(l,r,rt);
    if(L<=mid)update(L,R,val,l,mid,rt<<1);
    if(R>mid)update(L,R,val,mid+1,r,rt<<1|1);
    pushup(rt);
}
int query(int L,int R,int l,int r,int rt)
{
    if(L<=l&&r<=R)return sum[rt];
    int mid=(l+r)>>1,ans=0;
    pushdown(l,r,rt);
    if(L<=mid)ans=ans+query(L,R,l,mid,rt<<1);
    if(R>mid)ans=ans+query(L,R,mid+1,r,rt<<1|1);
    pushup(rt);
    return ans;
}
int main()
{
    int n=5;
    a[1]=5,a[2]=2,a[3]=1,a[4]=7,a[5]=4;
    build(1,n,1);
    update(1,4,5,1,n,1);
    printf("%d",query(3,5,1,n,1));
    return 0;
} 

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单点修改

#include<bits/stdc++.h>
using namespace std;

const int N=1e5+5;
int sum[N<<2],a[N];
void pushup(int rt)
{
    sum[rt]=sum[rt<<1]+sum[rt<<1|1];
    //      =max()
    //      =min()
    //      =gcd()
    //      =lcm()
}
void build(int l,int r,int rt)
{
    if(l==r)
    {
        sum[rt]=a[l];
        return;
    }
    int mid=(l+r)>>1;
    build(l,mid,rt<<1);
    build(mid+1,r,rt<<1|1);
    pushup(rt);
}
void update(int pos,int val,int l,int r,int rt)
{
    if(pos<=l&&r<=pos)
    {
        sum[rt]=val;
        return;
    }
    int mid=(l+r)>>1;
    if(pos<=mid)update(pos,val,l,mid,rt<<1);
    else update(pos,val,mid+1,r,rt<<1|1);
    pushup(rt);
}
int query(int L,int R,int l,int r,int rt)
{
    if(L<=l&&r<=R)return sum[rt];
    int mid=(l+r)>>1,ans=0;
    if(L<=mid)ans=ans+query(L,R,l,mid,rt<<1);
    if(R>mid)ans=ans+query(L,R,mid+1,r,rt<<1|1);
    pushup(rt);
    return ans;
}
int main()
{
    int n=5;
    a[1]=5,a[2]=2,a[3]=1,a[4]=7,a[5]=4;
    build(1,n,1);
    update(3,8,1,n,1);
    printf("%d",query(3,5,1,n,1));
    return 0;
} 

View Code

模板题:

　　https://www.luogu.org/problem/P3372

　　https://www.luogu.org/problem/P3373