【算法】二叉树深度优先搜索和广度优先搜索

一、深度优先搜索

function Tree(value) {
	this.value = value;
	this.left = null;
	this.right = null;
}
const a = new Tree("A");
const b = new Tree("B");
const c = new Tree("C");
const d = new Tree("D");
const e = new Tree("E");
const f = new Tree("F");
const g = new Tree("G");

a.left = b;
a.right = c;
b.left = d;
b.right = e;
c.left = f;
c.right = g;

// 对于二叉树，深度优先搜索和前序遍历的顺序是一样的
function deepSearch(root, target) {
	if(root == null) return false;
	if(root.value == target) return true;
	let left = deepSearch(root.left, target);
	let right = deepSearch(root.right, target);
	return left || right;
}
console.log(deepSearch(a, 'E'))

二、广度优先搜索

function wideSearch(rootList, target) {
	if(rootList == null) return false;
	let childList = [];
	for(let i = 0; i < rootList.length; i ++) {
		if(rootList[i] != null && rootList[i].value == target) {
			return true;
		}else {
			childList.push(rootList[i].left);
			childList.push(rootList[i].right);
		}
	}
	return wideSearch(childList, target);
}
console.log(wideSearch([a], 'E'))

深度优先搜索，先遍历左子树，再遍历右子树

广度优先搜索，相当于直接横向打印二叉树

深度优先搜索使用栈，先进后出

广度优先搜索使用队列，先进先出