AC at 1，3. other WA.在线等

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const LL Inf = 1e15;
const int maxn = 1e6 + 10;
LL tr[maxn << 1], lazy1[maxn << 1], lazy2[maxn << 1];
int lson[maxn << 1], rson[maxn << 1], tot;
int a[maxn];
void pushup(int k){
	tr[k] = max(tr[lson[k]], tr[rson[k]]);
}
void pushdown1(int l, int r, int k){
	if(lazy1[k]){
		int mid = (l + r) >> 1;
		tr[lson[k]] += (mid - l + 1) * lazy1[k];
		tr[rson[k]] += (r - mid) * lazy1[k];
		lazy1[lson[k]] += lazy1[k];
		lazy1[rson[k]] += lazy1[k];
		lazy1[k] = 0;
	}
}
void pushdown2(int k){
	if(lazy2[k] != Inf){
		tr[lson[k]] = lazy2[k];
		tr[rson[k]] = lazy2[k];
		lazy2[lson[k]] = lazy2[k];
		lazy2[rson[k]] = lazy2[k];
		lazy1[k] = 0;
		lazy1[lson[k]] = 0;
		lazy1[rson[k]] = 0;
		lazy2[k] = Inf;
	}
} 
void build(int l, int r, int &k){
	k = ++tot;
	lazy2[k] = Inf;
	if(l == r){
		tr[k] = a[l];
		return;
	}
	int mid = (l + r) >> 1;
	build(l , mid, lson[k]);
	build(mid + 1, r, rson[k]);
	pushup(k);
}
void update1(int l, int r, int L, int R, int k, LL x){
	if(l >= L && r <= R){
		tr[k] += (r - l + 1) * x;
		lazy1[k] += x;
		return;
	}
	pushdown2(k);
	pushdown1(l, r, k);
	int mid = (l + r) >> 1;
	if(L <= mid) update1(l, mid, L, R, lson[k], x);
	if(R > mid)	update1(mid + 1, r, L, R, rson[k], x);
	pushup(k);
}
void update2(int l, int r, int L, int R, int k, LL x){
	if(l >= L && r <= R){
		tr[k] =  x;
		lazy2[k] = x;
		lazy1[k] = 0;
		return;
	}
	pushdown2(k);
	pushdown1(l, r, k);
	int mid = (l + r) >> 1;
	if(L <= mid) update2(l, mid, L, R, lson[k], x);
	if(R > mid)	update2(mid + 1, r, L, R, rson[k], x);
	pushup(k);
}

LL getsum(int l, int r, int L, int R, int k){
	if(l >= L && r <= R){
		return tr[k];
	}
	pushdown2(k);
	pushdown1(l, r, k);
	int mid = (l + r) >> 1;
	LL sum = -Inf;
	if(L <= mid) sum = max(sum, getsum(l, mid, L, R, lson[k]));
	if(R > mid) sum = max(sum, getsum(mid + 1, r, L, R, rson[k]));
	return sum;
}
int n, q;
int main(){
	scanf("%d%d", &n, &q);
	for(int i = 1; i <= n; i++)
		scanf("%d", &a[i]);
	int tmp = 0;	
	build(1, n, tmp);
	while(q--){
		int op;
		scanf("%d", &op);
		if(op == 1){
			int L, R; LL x;
			scanf("%d%d%lld", &L, &R, &x);
			update2(1, n, L, R, 1, x);			
		}
		else if(op == 2){
			int L, R; LL x;
			scanf("%d%d%lld", &L, &R, &x);
			update1(1, n, L, R, 1, x);
		}
		else{
			int L, R;
			scanf("%d%d", &L, &R);
			printf("%lld\n", getsum(1, n, L, R, 1));
		}
	}	
}