二叉树的diff算法

function Node(value) {
    this.value = value;
    this.left = null;
    this.right = null;
}

let a1 = new Node('a');
let b1 = new Node('b');
let c1 = new Node('c');
let d1 = new Node('d');
let e1 = new Node('e');
let f1 = new Node('f');
let g1 = new Node('g');

a1.left = c1;
a1.right = b1;
c1.left = f1;
c1.right = g1;
b1.left = d1;
b1.right = e1;

let a2 = new Node('a');
let b2 = new Node('z');
let c2 = new Node('c');
let d2 = new Node('x');
let e2 = new Node('e');
let f2 = new Node('f');
let g2 = new Node('g');


a2.left = c2;
a2.right = b2;
c2.left = f2;
// c2.right = g2;
b2.left = d2;
b2.right = e2;
f2.right = g2;

// 比较是否二叉树是否相同
// function compareTree(root1, root2) {
//     if (root1 == root2) { // 是同一颗树
//         return true;
//     }
//     if (root1 == null && root2 != null || root2 == null && root1 != null) {
//         return false;
//     }
//     if (root1.value != root2.value) { // 相同位置的值不相等
//         return false;
//     }
//     let leftBoolen = compareTree(root1.left, root2.left);   // 判断左子树是否相等
//     let rightBoolen = compareTree(root1.right, root2.right);    // 判断右子树是否相等
//     return leftBoolen && rightBoolen;   // 必须左右子树都相等才算相等
// }

// 新增了什么，修改了什么，删除了什么

// { type: '新增', origin: null, now: c2 }
// { type: '修改', origin: c1, now: c2 }
// { type: '删除', origin: c2, now: null }

function diffTree(root1, root2, diffList) {
    if (root1 == root2) {
        return diffList;
    }
    if (root1 == null && root2 != null) {  // 新增
        diffList.push({
            type: "add",
            origin: null,
            now: root2
        });
    } else if (root1 != null && root2 == null) {   // 删除
        diffList.push({
            type: "delete",
            origin: root1,
            now: null
        });
    } else if (root1.value != root2.value) {   // 编辑
        diffList.push({
            type: "edit",
            origin: root1,
            now: root2
        });
        diffTree(root1.left, root2.left, diffList);
        diffTree(root1.right, root2.right, diffList);
    } else {
        diffTree(root1.left, root2.left, diffList);
        diffTree(root1.right, root2.right, diffList);
    }

}


let diffList = [];
diffTree(a1, a2, diffList);
console.log(diffList);