有如下二叉树
遍历:
// 前序遍历, head-left-right
function HLR (tree) {
const stack = [], res = []
if (tree) stack.push(tree)
while (stack.length) {
const cur = stack.pop()
res.push(cur.val)
// 栈先入后出,所以要先放入right
cur.right && stack.push(cur.right)
cur.left && stack.push(cur.left)
}
return res
}
// 中续遍历, left-head-right
function LHR (tree) {
const stack = [], res = []
let root = tree
while (true) {
while (root) {
stack.push(root)
root = root.left
}
if (stack.length === 0) break
const cur = stack.pop()
res.push(cur.val)
root = cur.right
}
return res
}
// 后续遍历, left-right-head
function LRH (tree) {
const stack = [], res = []
if (tree) stack.push(tree)
while (stack.length) {
const cur = stack.pop()
res.push(cur.val)
cur.left && stack.push(cur.left)
cur.right && stack.push(cur.right)
}
return res.reverse()
}
// 层次遍历
function order (tree) {
const queue = [], res = []
if (tree) queue.push(tree)
while (queue.length) {
const cur = queue.shift()
res.push(cur.val)
cur.left && queue.push(cur.left)
cur.right && queue.push(cur.right)
}
return res
}
console.log('前序遍历:', HLR(tree));
console.log('中序遍历:', LHR(tree));
console.log('后序遍历:', LRH(tree));
console.log('层次遍历:', order(tree));
结果: