day82（2.10）——leetcode面试经典150

努力学算法的蒟蒻2026-02-11 16:08
427. 建立四叉树
这个题目把我吓到了哈哈哈如此之多
题目：

题解：

java 复制代码
/*
// Definition for a QuadTree node.
class Node {
    public boolean val;
    public boolean isLeaf;
    public Node topLeft;
    public Node topRight;
    public Node bottomLeft;
    public Node bottomRight;

    
    public Node() {
        this.val = false;
        this.isLeaf = false;
        this.topLeft = null;
        this.topRight = null;
        this.bottomLeft = null;
        this.bottomRight = null;
    }
    
    public Node(boolean val, boolean isLeaf) {
        this.val = val;
        this.isLeaf = isLeaf;
        this.topLeft = null;
        this.topRight = null;
        this.bottomLeft = null;
        this.bottomRight = null;
    }
    
    public Node(boolean val, boolean isLeaf, Node topLeft, Node topRight, Node bottomLeft, Node bottomRight) {
        this.val = val;
        this.isLeaf = isLeaf;
        this.topLeft = topLeft;
        this.topRight = topRight;
        this.bottomLeft = bottomLeft;
        this.bottomRight = bottomRight;
    }
}
*/

class Solution {
    public Node construct(int[][] grid) {
        int n = grid.length;
        return build(grid, 0, n-1, 0, n-1);
    }

    Node build(int[][] grid, int l1, int r1, int l2, int r2) {
        int flag = 0;
        int d = grid[l1][l2];
        for(int i=l1;i<=r1;i++) {
            for(int j=l2;j<=r2;j++) {
                if(grid[i][j]!=d) {
                    flag=1;
                    break;
                }
            }
            if(flag==1) {
                break;
            }
        }

        //如果该区域都相等，直接返回Node
        if(flag==0) {
            return new Node(d == 1, true);
        }

        int mid1 = (l1+r1)/2;
        int mid2 = (l2+r2)/2;

        Node tL = build(grid, l1, mid1, l2, mid2);
        Node tR = build(grid, l1, mid1, mid2+1, r2);
        Node bL = build(grid, mid1+1, r1, l2, mid2);
        Node bR = build(grid, mid1+1, r1, mid2+1, r2);
       
        return new Node(false, false, tL, tR, bL, bR);
    }
}