最大数（线段树）

Posted 2022-06-09 loganacmer

最大数

 

题目思路：

　　入门题，每加入一个数就在树中单点修改一次，注意加入时要加上上一次查询的答案。

#include<bits/stdc++.h>
#define ll long long
using namespace std;
void push_down(int p,int v);
typedef struct segment

    int left,right;
    int lazy;
    int max;
    segment()
    
        lazy = -1;
    
T;
T tree[4*200010];
ll n,m,a[200010],p;
void build(int p,int l,int r)

    tree[p].left = l,tree[p].right = r;
    if(l==r)
    
        tree[p].max = a[l];        
        return ;
    
    int mid = (l+r)/2;
    build(p*2,l,mid);
    build(p*2+1,mid+1,r);
    tree[p].max = max(tree[2*p].max,tree[2*p+1].max);

int query(int p,int l,int r)
//cout<<p<<" "<<l<<" "<<r<<" "<<tree[p].left<<" "<<tree[p].right<<endl;
    int inf = -100000007;
    if(l<=tree[p].left&&r>=tree[p].right)    
        return tree[p].max;
    push_down(p,tree[p].lazy);
    int mid = (tree[p].left+tree[p].right)/2;
    if(l<=mid)
        inf = max(inf,query(p*2,l,r));
    if(mid<r)
        inf = max(inf,query(p*2+1,l,r));
    return inf;
        

void change(int p,int x,int v)//单点修改

    if(tree[p].left==tree[p].right)
    
        tree[p].max = v;
        return ;
    
    int mid = (tree[p].left+tree[p].right)/2;
    if(x<=mid)
        change(p*2,x,v);
    else
        change(p*2+1,x,v);
    tree[p].max = max(tree[p*2].max,tree[p*2+1].max);

void push_down(int p,int v)

    if(tree[p].lazy==-1)
        return ;
    tree[p*2].max = v;
    tree[p*2+1].max = v;
    tree[p*2].lazy = v;
    tree[p*2+1].lazy = v;


void change2(int p,int l,int r,int v)//区间修改

    if(l<=tree[p].left&&r>=tree[p].right)    
    
        tree[p].max = v;
        if(tree[p].left!=tree[p].right)
            tree[p].lazy = v;
        return ;
    
    push_down(p,tree[p].lazy);
    int mid = (tree[p].left+tree[p].right)/2;
    if(l<=mid)
        change2(p*2,l,r,v);
    if(mid<r)
        change2(p*2+1,l,r,v);
    tree[p].max = max(tree[p*2].max,tree[p*2+1].max);

int main()

    char c;
    ll c1,c2,c3,last = 0,sum = 0;
    cin>>m>>p;
    build(1,1,200001);
    for(int i = 0;i<m;i++)
    
        cin>>c>>c1;
        if(c==‘A‘)
        
            sum++;
            change(1,sum,(c1+last)%p);
        
        else
        
            last = query(1,sum-c1+1,sum);
            cout<<last<<endl;
        
    
    return 0;