2236.cpp

#include <stdio.h>
#include <iostream>
#include <algorithm>
using namespace std;

#define N 100005
#define oo 999999999
#define ll long long

ll t[4*N], Lazy[4*N]; // one-based

void push_down(int Node, int a, int b){
    if (Lazy[Node] != -oo) {
        if (a!=b){
            Lazy[Node*2] = Lazy[Node];
            Lazy[Node*2+1] = Lazy[Node];
        }
        t[Node] = Lazy[Node] * (b-a+1);
        Lazy[Node] = -oo;
    }
}

void update(int Node, int a, int b, int i, int j, ll Value){
    push_down(Node, a, b);
    if (i>j || a>j || i>b) return ;
    if (i<=a && b<=j) {
        Lazy[Node] = Value;
        push_down(Node, a, b);
        return ;
    }
    update(Node*2, a, (a+b)/2, i, j, Value);
    update(Node*2+1, (a+b)/2+1, b, i, j, Value);
    t[Node] = t[Node*2] + t[Node*2+1];
}

ll query(int Node, int a, int b, int i, int j){
    push_down(Node, a, b);
    if (i>j || a>j || i>b) return 0;
    if (i<=a && b<=j) return t[Node];
    ll q1 = query(Node*2, a, (a+b)/2, i, j);
    ll q2 = query(Node*2+1, (a+b)/2+1, b, i, j);
    return q1 + q2;
}

main(){
    int n = 4;
    for (int i=0; i<n; i++) update(1, 0, n-1, i, i, i+1); // build
    update(1, 0, n-1, 0, 3, 2);
    cout << query(1, 0, n-1, 0, 3) << endl;
}