力扣 剑指 Offer 65.68

异或运算能做出没有进位的加法，而与运算可以得到加法的进位

class Solution {
    public int add(int a, int b) {
        while(b!=0){
            int c = (a & b) << 1;
            a ^= b;
            b = c;
        }
        return a;
    }
}

二叉树的递归总会有极简而又神奇的写法

class Solution {
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if(root==null||p==root||q==root) return root;
        TreeNode left = lowestCommonAncestor(root.left,p,q);
        TreeNode right = lowestCommonAncestor(root.right,p,q);
        if(left==null) return right;
        if(right==null) return left;
        return root;
    }
}