【leetcode https://leetcode.cn/problems/count-integers-in-intervals/】 线段树

leetccode count-integers-in-intervals 线段树解决：

class CountIntervals {
    Seg root;

    public CountIntervals() {
        root = new Seg(1, 1000000000);
    }

    public void add(int left, int right) {
        root.add(left, right);
    }

    public int count() {
        return root.cnt;
    }

    public static void main(String[] args) {
        CountIntervals countIntervals = new CountIntervals();
        System.out.println(countIntervals.count());
        countIntervals.add(39, 44);

        System.out.println(countIntervals.count());
        countIntervals.add(13, 49);
        System.out.println(countIntervals.count());
        System.out.println(countIntervals.count());
        countIntervals.add(47, 50);
    }

    class Seg {
        int cl, cr;
        int cnt;
        boolean tag;
        Seg l, r;

        public Seg(final int cl, final int cr) {
            this.cl = cl;
            this.cr = cr;
            // this.cnt = cr - cl + 1;
            this.cnt = 0;
            this.tag = false;
        }

        public void pushdown() {
            if (this.tag) {
                int mid = (cl + cr) >> 1;
                if (this.l == null) {
                    this.l = new Seg(cl, mid);
                }
                if (this.r == null) {
                    this.r = new Seg(mid + 1, cr);
                }
                this.l.tag = true;
                this.r.tag = true;
                this.l.cnt = mid - cl + 1;
                this.r.cnt = cr - mid;
            }
        }

        public void pushup() {
            /// this.cnt = 0;

            this.tag = this.l.tag & this.r.tag;
            this.cnt = this.l.cnt + this.r.cnt;

        }

        public void add(int L, int R) {
            if (cl == L && cr == R) {
                this.tag = true;
                this.cnt = R - L + 1;
                return;
            }

            if (this.tag) {
                return;
            }

            //      pushdown();
            int mid = (cl + cr) >> 1;
            if (this.r == null) {
                this.r = new Seg(mid + 1, cr);
            }
            if (this.l == null) {
                this.l = new Seg(cl, mid);
            }
            if (R <= mid) {
                this.l.add(L, R);
            } else {
                if (L > mid) {//再右边加入
                    this.r.add(L, R);
                } else {
                    this.l.add(L, mid);
                    this.r.add(mid + 1, R);
                }
            }
            pushup();
        }
    }
}

/**
 * Your CountIntervals object will be instantiated and called as such:
 * CountIntervals obj = new CountIntervals();
 * obj.add(left,right);
 * int param_2 = obj.count();
 */