【699. 掉落的方块】线段树

import java.util.ArrayList;
import java.util.List;

class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution();
        System.out.println(solution.fallingSquares(new int[][]{
                {9,7},{1,9},{3,1}
        }));
    }
    public List<Integer> fallingSquares(int[][] positions) {
        Seg seg = new Seg(1,101000000);
        List<Integer> ans = new ArrayList<>();
        for(int[] position:positions){
            int l = position[0];
            int r = position[0] +position[1] - 1;
            int curr = seg.query(l,r);
            seg.update(l,r,curr+position[1]);
            ans.add(seg.height);
        }
        return ans;
    }
    class Seg{
        int cl,cr;
        Seg left,right;
        int lazy;
        int height;

        public Seg(int l,int r){
            this.cl = l;
            this.cr = r;
            this.height = 0;
        }

        public int query(int l,int r){
            if( cl == l && cr == r){
                return this.height;
            }
            pushdown();
            int mid = (cl+cr)/2;
            if( r<=mid){
                return this.left.query(l,r);
            }
            else{
                if( l > mid){
                    return this.right.query(l,r);
                }else{
                    return Math.max(this.left.query(l,mid),this.right.query(mid+1,r));
                }
            }
        }


        public void pushdown() {
            int mid = (cl+cr)/2;
            if( this.left == null){
                this.left = new Seg(cl,mid);
            }
            if(this.right == null){
                this.right = new Seg(mid+1,cr);
            }
            if(this.lazy == 0) return;
            this.left.lazy = this.lazy; this.right.lazy = this.lazy;
            this.left.height = this.lazy;
            this.right.height = this.lazy;
            this.lazy = 0;
        }

        public void pushup(){
            this.height = Math.max(this.left.height,this.right.height);
        }

        public void update(int l,int r,int height){
            if(cl == l && cr == r){
                this.height = height;
                this.lazy = height;
                return;
            }
            pushdown();
            int mid = (cl+cr)/2;
            if(r<=mid){
                this.left.update(l,r,height);
            }else{
                if(l>mid){
                    this.right.update(l,r,height);
                }else{
                    this.left.update(l,mid,height);
                    this.right.update(mid+1,r,height);
                }
            }
            pushup();
        }
    }
}