diff --git a/problems/0100.相同的树.md b/problems/0100.相同的树.md index c40f79fd..31a68692 100644 --- a/problems/0100.相同的树.md +++ b/problems/0100.相同的树.md @@ -139,29 +139,29 @@ public: ## 迭代法 ```C++ -lass Solution { +class Solution { public: bool isSameTree(TreeNode* p, TreeNode* q) { if (p == NULL && q == NULL) return true; if (p == NULL || q == NULL) return false; queue que; - que.push(p); // - que.push(q); // + que.push(p); // 添加根节点p + que.push(q); // 添加根节点q while (!que.empty()) { // TreeNode* leftNode = que.front(); que.pop(); TreeNode* rightNode = que.front(); que.pop(); - if (!leftNode && !rightNode) { // + if (!leftNode && !rightNode) { // 若p的节点与q的节点都为空 continue; } - // + // 若p的节点与q的节点有一个为空或p的节点的值与q节点不同 if ((!leftNode || !rightNode || (leftNode->val != rightNode->val))) { return false; } - que.push(leftNode->left); // - que.push(rightNode->left); // - que.push(leftNode->right); // - que.push(rightNode->right); // + que.push(leftNode->left); // 添加p节点的左子树节点 + que.push(rightNode->left); // 添加q节点的左子树节点点 + que.push(leftNode->right); // 添加p节点的右子树节点 + que.push(rightNode->right); // 添加q节点的右子树节点 } return true; } @@ -173,23 +173,71 @@ public: Java： ```java +// 递归法 class Solution { public boolean isSameTree(TreeNode p, TreeNode q) { - if (p == null && q == null) { - return true; - } else if (q == null || p == null) { - return false; - } else if (q.val != p.val) { - return false; - } else { - return isSameTree(q.left, p.left) && isSameTree(q.right, p.right); - } + if (p == null && q == null) return true; + else if (q == null || p == null) return false; + else if (q.val != p.val) return false; + return isSameTree(q.left, p.left) && isSameTree(q.right, p.right); } } +``` +```java +// 迭代法 +class Solution { + public boolean isSameTree(TreeNode p, TreeNode q) { + if(p == null && q == null) return true; + if(p == null || q == null) return false; + Queue que= new LinkedList(); + que.offer(p); + que.offer(q); + while(!que.isEmpty()){ + TreeNode leftNode = que.poll(); + TreeNode rightNode = que.poll(); + if(leftNode == null && rightNode == null) continue; + if(leftNode == null || rightNode== null || leftNode.val != rightNode.val) return false; + que.offer(leftNode.left); + que.offer(rightNode.left); + que.offer(leftNode.right); + que.offer(rightNode.right); + } + return true; + } +} ``` Python： +```python +# 递归法 +class Solution: + def isSameTree(self, p: TreeNode, q: TreeNode) -> bool: + if not p and not q: return True + elif not p or not q: return False + elif p.val != q.val: return False + return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right) +``` +```python +# 迭代法 +class Solution: + def isSameTree(self, p: TreeNode, q: TreeNode) -> bool: + if not p and not q: return True + if not p or not q: return False + que = collections.deque() + que.append(p) + que.append(q) + while que: + leftNode = que.popleft() + rightNode = que.popleft() + if not leftNode and not rightNode: continue + if not leftNode or not rightNode or leftNode.val != rightNode.val: return False + que.append(leftNode.left) + que.append(rightNode.left) + que.append(leftNode.right) + que.append(rightNode.right) + return True +``` Go： JavaScript： diff --git a/problems/0121.买卖股票的最佳时机.md b/problems/0121.买卖股票的最佳时机.md index 259fff34..8ad6c8c6 100644 --- a/problems/0121.买卖股票的最佳时机.md +++ b/problems/0121.买卖股票的最佳时机.md @@ -313,6 +313,26 @@ func max(a,b int)int { } ``` +JavaScript： + +```javascript +const maxProfit = prices => { + const len = prices.length; + // 创建dp数组 + const dp = new Array(len).fill([0, 0]); + // dp数组初始化 + dp[0] = [-prices[0], 0]; + for (let i = 1; i < len; i++) { + // 更新dp[i] + dp[i] = [ + Math.max(dp[i - 1][0], -prices[i]), + Math.max(dp[i - 1][1], prices[i] + dp[i - 1][0]), + ]; + } + return dp[len - 1][1]; +}; +``` + diff --git a/problems/0337.打家劫舍III.md b/problems/0337.打家劫舍III.md index 197841e9..780e4aef 100644 --- a/problems/0337.打家劫舍III.md +++ b/problems/0337.打家劫舍III.md @@ -368,7 +368,32 @@ class Solution: return (val1, val2) ``` -Go： +JavaScript： + +> 动态规划 + +```javascript +const rob = root => { + // 后序遍历函数 + const postOrder = node => { + // 递归出口 + if (!node) return [0, 0]; + // 遍历左子树 + const left = postOrder(node.left); + // 遍历右子树 + const right = postOrder(node.right); + // 不偷当前节点，左右子节点都可以偷或不偷，取最大值 + const DoNot = Math.max(left[0], left[1]) + Math.max(right[0], right[1]); + // 偷当前节点，左右子节点只能不偷 + const Do = node.val + left[0] + right[0]; + // [不偷，偷] + return [DoNot, Do]; + }; + const res = postOrder(root); + // 返回最大值 + return Math.max(...res); +}; +``` diff --git a/problems/0347.前K个高频元素.md b/problems/0347.前K个高频元素.md index 6b07c258..161df1ad 100644 --- a/problems/0347.前K个高频元素.md +++ b/problems/0347.前K个高频元素.md @@ -190,6 +190,101 @@ class Solution: Go： +javaScript: +```js +/** + * @param {number[]} nums + * @param {number} k + * @return {number[]} + */ +var topKFrequent = function(nums, k) { + const map = new Map(); + + for(const num of nums) { + map.set(num, (map.get(num) || 0) + 1); + } + + // 创建小顶堆 + const priorityQueue = new PriorityQueue((a, b) => a[1] - b[1]); + + // entry 是一个长度为2的数组，0位置存储key，1位置存储value + for (const entry of map.entries()) { + priorityQueue.push(entry); + if (priorityQueue.size() > k) { + priorityQueue.pop(); + } + } + + const ret = []; + + for(let i = priorityQueue.size() - 1; i >= 0; i--) { + ret[i] = priorityQueue.pop()[0]; + } + + return ret; +}; + + +function PriorityQueue(compareFn) { + this.compareFn = compareFn; + this.queue = []; +} + +// 添加 +PriorityQueue.prototype.push = function(item) { + this.queue.push(item); + let index = this.queue.length - 1; + let parent = Math.floor((index - 1) / 2); + // 上浮 + while(parent >= 0 && this.compare(parent, index) > 0) { + // 交换 + [this.queue[index], this.queue[parent]] = [this.queue[parent], this.queue[index]]; + index = parent; + parent = Math.floor((index - 1) / 2); + } +} + +// 获取堆顶元素并移除 +PriorityQueue.prototype.pop = function() { + const ret = this.queue[0]; + + // 把最后一个节点移到堆顶 + this.queue[0] = this.queue.pop(); + + let index = 0; + // 左子节点下标，left + 1 就是右子节点下标 + let left = 1; + let selectedChild = this.compare(left, left + 1) > 0 ? left + 1 : left; + + // 下沉 + while(selectedChild !== undefined && this.compare(index, selectedChild) > 0) { + // 交换 + [this.queue[index], this.queue[selectedChild]] = [this.queue[selectedChild], this.queue[index]]; + index = selectedChild; + left = 2 * index + 1; + selectedChild = this.compare(left, left + 1) > 0 ? left + 1 : left; + } + + return ret; +} + +PriorityQueue.prototype.size = function() { + return this.queue.length; +} + +// 使用传入的 compareFn 比较两个位置的元素 +PriorityQueue.prototype.compare = function(index1, index2) { + if (this.queue[index1] === undefined) { + return 1; + } + if (this.queue[index2] === undefined) { + return -1; + } + + return this.compareFn(this.queue[index1], this.queue[index2]); +} +``` + ----------------------- diff --git a/problems/0701.二叉搜索树中的插入操作.md b/problems/0701.二叉搜索树中的插入操作.md index 61027453..1ec80da1 100644 --- a/problems/0701.二叉搜索树中的插入操作.md +++ b/problems/0701.二叉搜索树中的插入操作.md @@ -255,7 +255,7 @@ class Solution { Python： -递归法 +**递归法** - 有返回值 ```python class Solution: @@ -268,7 +268,63 @@ class Solution: root.left = self.insertIntoBST(root.left, val) # 递归创建左子树 return root ``` +**递归法** - 无返回值 +```python +class Solution: + def insertIntoBST(self, root: TreeNode, val: int) -> TreeNode: + if not root: + return TreeNode(val) + parent = None + def __traverse(cur: TreeNode, val: int) -> None: + # 在函数运行的同时把新节点插入到该被插入的地方. + nonlocal parent + if not cur: + new_node = TreeNode(val) + if parent.val < val: + parent.right = new_node + else: + parent.left = new_node + return + parent = cur # 重点: parent的作用只有运行到上面if not cur:才会发挥出来. + if cur.val < val: + __traverse(cur.right, val) + else: + __traverse(cur.left, val) + return + __traverse(root, val) + return root +``` +**迭代法** +与无返回值的递归函数的思路大体一致 +```python +class Solution: + def insertIntoBST(self, root: TreeNode, val: int) -> TreeNode: + if not root: + return TreeNode(val) + parent = None + cur = root + + # 用while循环不断地找新节点的parent + while cur: + if cur.val < val: + parent = cur + cur = cur.right + elif cur.val > val: + parent = cur + cur = cur.left + + # 运行到这意味着已经跳出上面的while循环, + # 同时意味着新节点的parent已经被找到. + # parent已被找到, 新节点已经ready. 把两个节点黏在一起就好了. + if parent.val > val: + parent.left = TreeNode(val) + else: + parent.right = TreeNode(val) + + return root + +``` Go： diff --git a/problems/背包问题理论基础完全背包.md b/problems/背包问题理论基础完全背包.md index 1ad09c4b..0417005b 100644 --- a/problems/背包问题理论基础完全背包.md +++ b/problems/背包问题理论基础完全背包.md @@ -311,7 +311,38 @@ func main() { fmt.Println(test_CompletePack2(weight, price, 4)) } ``` +Javascript: +```Javascript +// 先遍历物品，再遍历背包容量 +function test_completePack1() { + let weight = [1, 3, 5] + let value = [15, 20, 30] + let bagWeight = 4 + let dp = new Array(bagWeight + 1).fill(0) + for(let i = 0; i <= weight.length; i++) { + for(let j = weight[i]; j <= bagWeight; j++) { + dp[j] = Math.max(dp[j], dp[j - weight[i]] + value[i]) + } + } + console.log(dp) +} +// 先遍历背包容量，再遍历物品 +function test_completePack2() { + let weight = [1, 3, 5] + let value = [15, 20, 30] + let bagWeight = 4 + let dp = new Array(bagWeight + 1).fill(0) + for(let j = 0; j <= bagWeight; j++) { + for(let i = 0; i < weight.length; i++) { + if (j >= weight[i]) { + dp[j] = Math.max(dp[j], dp[j - weight[i]] + value[i]) + } + } + } + console.log(2, dp); +} +``` -----------------------