feat: 二叉树最近公共祖先

二叉树/二叉树的最近公共祖先.js

@@ -0,0 +1,57 @@
+let T = require("../工具/二叉树")
+
+let lowestCommonAncestor = function (root, p, q) {
+  let findAndCreate = (node, target, depth) => {
+    if (node !== target) {
+      let findInLeft
+      if (node.left) {
+        node.left.parent = node
+        findInLeft = findAndCreate(node.left, target, depth + 1)
+      }
+
+      if (findInLeft) {
+        return findInLeft
+      } else {
+        if (node.right) {
+          node.right.parent = node
+          return findAndCreate(node.right, target, depth + 1)
+        }
+      }
+    } else {
+      return {
+        depth,
+        node,
+      }
+    }
+  }
+
+  let findP = findAndCreate(root, p, 0) || {}
+  let findQ = findAndCreate(root, q, 0) || {}
+
+  let cur = findP.depth > findQ.depth ? findQ.node : findP.node
+
+  while (!(isAncestor(cur, p) && isAncestor(cur, q))) {
+    cur = cur.parent
+  }
+
+  return cur
+}
+
+function isAncestor(node, target) {
+  if (!node) {
+    return false
+  }
+  if (node !== target) {
+    return !!(isAncestor(node.left, target) || isAncestor(node.right, target))
+  } else {
+    return true
+  }
+}
+
+let l
+let r
+let t = new T(3)
+t.left = l = new T(5)
+t.right = r = new T(1)
+
+console.log(lowestCommonAncestor(t, l, r))