WA on #1 #3，线段树玄关求调

P1253 扶苏的问题

#include<iostream>
#define bitset(x) x & (-x)
#define int long long
using namespace std;

int n, m, a[1000005];

struct node
{
    int l, r, flag, sum, cover;
} tree[4000005];

void build(int i, int l, int r)
{
    tree[i].flag = 1e18 + 5;
    tree[i].l = l, tree[i].r = r;
    if(l == r)
    {
        tree[i].sum = a[i];
        return ;
    }
    int mid = l + r >> 1;
    build(i << 1, l, mid);
    build(i << 1 | 1, mid + 1, r);
    tree[i].sum = max(tree[i << 1].sum, tree[i << 1 | 1].sum);
    return ;
}

void pushdown(int i)
{
    if(tree[i].flag != 1e18 + 5)
    {
        tree[i << 1].flag = tree[i << 1 | 1].flag = tree[i].flag;
        tree[i << 1].cover = tree[i << 1 | 1].cover = 0;
        tree[i << 1].sum = tree[i << 1 | 1].sum = tree[i].flag;
        tree[i].flag = 1e18 + 5;
    }
    if(tree[i].cover)
    {
        tree[i << 1].cover += tree[i].cover;
        tree[i << 1 | 1].cover += tree[i].cover;
        tree[i << 1].sum += tree[i].cover;
        tree[i << 1 | 1].sum += tree[i].cover;
        tree[i].cover = 0;
        return ;
    }
}

void add(int i, int l, int r, int k)
{
    if(l <= tree[i].l && tree[i].r <= r)
    {
        tree[i].flag += k;
        tree[i].sum += k;
        return ;
    }
    int mid = tree[i].l + tree[i].r >> 1;
    pushdown(i);
    if(l <= mid) add(i << 1, l, r, k);
    if(r >= mid + 1) add(i << 1 | 1, l, r, k);
    tree[i].sum = tree[i << 1].sum + tree[i << 1 | 1].sum;
}

int find(int i, int l, int r)
{
    if(tree[i].l >= l && tree[i].r <= r)
    {
        return tree[i].sum;
    }
    pushdown(i);
    int mid = tree[i].l + tree[i].r >> 1, ans = -1e18;
    if(l <= mid) ans = max(find(i << 1, l, r), ans);
    if(r >= mid + 1) ans = max(find(i << 1 | 1, l, r), ans);
    return ans;
}

void change(int i, int l, int r, int x)
{
    if(l <= tree[i].l && tree[i].r <= r)
    {
        tree[i].cover = x;
        tree[i].sum = x;
        tree[i].flag = 0;
        return ;
    }
    int mid = tree[i].l + tree[i].r >> 1;
    pushdown(i);
    if(l <= mid)
    {
        change(i << 1, l, r, x);
    }
    if(mid + 1 <= r)
    {
        change(i << 1 | 1, l, r, x);
    }
    tree[i].sum = max(tree[i << 1].sum, tree[i << 1 | 1].sum);
}

signed main()
{
    cin >> n >> m;
    for(int i = 1; i <= n; i ++)
    {
        cin >> a[i];
    }

    build(1, 1, n);

    for(int i = 1; i <= m; i ++)
    {
        int op, x, y, k;
        cin >> op >> x >> y;

        if(op == 1)
        {
            cin >> k;
            change(1, x, y, k);
        }
        if(op == 2)
        {
            cin >> k;
            add(1, x, y, k);
        }
        if(op == 3)
        {
            cout << find(1, x, y) << endl;
        }
    }
    return 0;
}