RMQ

struct SegTree {
    int n;
    vector<int> a;
    vector<int> tree, add;

    SegTree(int n) {
        this->n = n;
        tree.resize(4 * n, 0);
        add.resize(4 * n, -1);
        a.resize(n, 0);
        build(0, 0, n);
    }

    void push(int v, int l, int r) {
        if (add[v] != -1 && l + 1 != r) {
            tree[v] = add[v];
            add[2 * v + 1] = add[v];
            add[2 * v + 2] = add[v];
            add[v] = -1;
        }
    }

    void build(int i, int l, int r) {
        add[i] = -1;
        if (l + 1 == r) {
            //tree[i] = a[l];
            tree[i] = 0;
        } else {
            int m = (l + r) / 2;
            build(2 * i + 1, l, m);
            build(2 * i + 2, m, r);
            tree[i] = (tree[i * 2 + 1] | tree[i * 2 + 2]);
        }
    }

    void _update(int i, int l, int r, int ql, int qr, int val) {
        if (qr <= l || ql >= r) {
            return;
        }
        if (ql <= l && qr >= r) {
            add[i] = val;
            push(i, l, r);
        } else {
            int m = (l + r) / 2;
            push(i, l, r);
            _update(i * 2 + 1, l, m, ql, qr, val);
            _update(i * 2 + 2, m, r, ql, qr, val);
            tree[i] = (tree[2 * i + 1] | tree[2 * i + 2]);
        }
    }

    int _get(int i, int l, int r, int ql, int qr) {
        if (qr <= l || ql >= r) {
            return 0;
        }
        push(i, l, r);
        if (ql <= l && qr >= r) {
            return tree[i];
        }
        int m = (l + r) / 2;
        return (_get(2 * i + 1, l, m, ql, qr) | _get(2 * i + 2, m, r, ql, qr));
    }

    int get(int ql, int qr) {
        return _get(0, 0, n, ql, qr);
    }

    void update(int ql, int qr, int val) {
        _update(0, 0, n, ql, qr, val);
    }
};