Shared code

#include<iostream>
#include<cassert>
#define ll long long
#define ull unsigned long long

using namespace std;

int q;

int n;
const int N = 200000;

int A[N + 1];

struct node {
	ll sum;
	ll lz_add;
	ll lz_set;
	node() {}
} t[N << 2];

void pushUp(int i) {
	t[i].sum = t[i<<1].sum + t[i<<1|1].sum;
}

void pushDown(int i, int l, int r) {
	int m = l + (r - l) / 2;
	if (t[i].lz_set) {
		t[i<<1].lz_set = t[i<<1|1].lz_set = t[i].lz_set;
		t[i<<1].sum = t[i].lz_set * (m - l + 1);
		t[i<<1|1].sum = t[i].lz_set * (r - m);
		t[i<<1].lz_add = t[i<<1|1].lz_add = 0;
		t[i].lz_set = 0;
	}
	else if (t[i].lz_add) {
		if (t[i<<1].lz_set) {
			t[i<<1].lz_set += t[i].lz_add;
		}
		else
			t[i<<1].lz_add += t[i].lz_add;
			
		t[i<<1].sum += t[i].lz_add * (m - l + 1);
		
		if (t[i<<1|1].lz_set) {
			t[i<<1|1].lz_set += t[i].lz_add;
		}
		else
			t[i<<1|1].lz_add += t[i].lz_add;
			
		t[i<<1|1].sum += t[i].lz_add * (r - m);
		
		t[i].lz_add = 0;
	}
}

void build(int i, int l, int r) {
	t[i].lz_add = 0;
	t[i].lz_set = 0;
	if (l == r) {
		t[i].sum = A[l];
	}
	else {
		int m = l + (r - l) / 2;
		build(i<<1, l, m);
		build(i<<1|1, m + 1, r);
		t[i].sum = t[i<<1].sum + t[i<<1|1].sum;
	}
}


void add(int i, int l, int r, int a, int b, ll x) {
	if (a > b) {
		return;
	}
	else if (l == a && r == b) {
		if (t[i].lz_set) {
			t[i].lz_set += x;
		}
		else {
			t[i].lz_add += x;
		}
		t[i].sum += x * (r - l + 1);
	}
	else {
		pushDown(i, l, r);
		
		int m = l + (r - l) / 2;
		add(i<<1, l, m, a, min(b, m), x);
		add(i<<1|1, m + 1, r, max(a, m + 1), b, x);
		
		pushUp(i);
	}
}

void set(int i, int l, int r, int a, int b, ll x) {
	if (a > b)
		return;
	else if (l == a && r == b) {
		t[i].lz_add = 0;
		t[i].lz_set = x;
		t[i].sum = x * (r - l + 1);
	}
	else {
		pushDown(i, l, r);
		
		int m = l + (r - l) / 2;
		set(i<<1, l, m, a, min(b, m), x);
		set(i<<1|1, m + 1, r, max(a, m + 1), b, x);
		
		pushUp(i);
	}
}


ll sum(int i, int l, int r, int a, int b) {
	if (a > b)
		return 0;
	else if (a == l && r == b) {
		return t[i].sum;
	}
	else {
		pushDown(i, l, r);
		
		int m = l + (r - l) / 2;
		return sum(i<<1, l, m, a, min(b, m))
			+ sum(i<<1|1, m + 1, r, max(a, m + 1), b);
	}
}


int main() {
	cin >> n >> q;
	
	for (int i = 1; i <= n; ++i) cin >> A[i];
	
	build(1, 1, n);
	
	int flag, a, b, x;
	while (q--) {
		cin >> flag >> a >> b;
		
		if (flag == 1) {
			cin >> x;
			add(1, 1, n, a, b, x);	
		}
		else if (flag == 2) {
			cin >> x;
			set(1, 1, n, a, b, x);
		}
		else {
			cout << sum(1, 1, n, a, b) << '\n';
		}
	}
}