[pull] master from youngyangyang04:master #22

Original file line number	Diff line number	Diff line change
Expand Up		@@ -646,5 +646,68 @@ func countNodes(_ root: TreeNode?) -> Int {
		}
		```

	## Scala

	递归:
	```scala
	object Solution {
	def countNodes(root: TreeNode): Int = {
	if(root == null) return 0
	1 + countNodes(root.left) + countNodes(root.right)
	}
	}
	```

	层序遍历:
	```scala
	object Solution {
	import scala.collection.mutable
	def countNodes(root: TreeNode): Int = {
	if (root == null) return 0
	val queue = mutable.Queue[TreeNode]()
	var node = 0
	queue.enqueue(root)
	while (!queue.isEmpty) {
	val len = queue.size
	for (i <- 0 until len) {
	node += 1
	val curNode = queue.dequeue()
	if (curNode.left != null) queue.enqueue(curNode.left)
	if (curNode.right != null) queue.enqueue(curNode.right)
	}
	}
	node
	}
	}
	```

	利用完全二叉树性质:
	```scala
	object Solution {
	def countNodes(root: TreeNode): Int = {
	if (root == null) return 0
	var leftNode = root.left
	var rightNode = root.right
	// 向左向右往下探
	var leftDepth = 0
	while (leftNode != null) {
	leftDepth += 1
	leftNode = leftNode.left
	}
	var rightDepth = 0
	while (rightNode != null) {
	rightDepth += 1
	rightNode = rightNode.right
	}
	// 如果相等就是一个满二叉树
	if (leftDepth == rightDepth) {
	return (2 << leftDepth) - 1
	}
	// 如果不相等就不是一个完全二叉树,继续向下递归
	countNodes(root.left) + countNodes(root.right) + 1
	}
	}
	```

		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

30 changes: 30 additions & 0 deletions problems/0257.二叉树的所有路径.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -702,5 +702,35 @@ func binaryTreePaths(_ root: TreeNode?) -> [String] {
		}
		```

	Scala:

	递归:
	```scala
	object Solution {
	import scala.collection.mutable.ListBuffer
	def binaryTreePaths(root: TreeNode): List[String] = {
	val res = ListBuffer[String]()
	def traversal(curNode: TreeNode, path: ListBuffer[Int]): Unit = {
	path.append(curNode.value)
	if (curNode.left == null && curNode.right == null) {
	res.append(path.mkString("->")) // mkString函数: 将数组的所有值按照指定字符串拼接
	return // 处理完可以直接return
	}

	if (curNode.left != null) {
	traversal(curNode.left, path)
	path.remove(path.size - 1)
	}
	if (curNode.right != null) {
	traversal(curNode.right, path)
	path.remove(path.size - 1)
	}
	}
	traversal(root, ListBuffer[Int]())
	res.toList
	}
	}
	```

		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

26 changes: 15 additions & 11 deletions problems/0494.目标和.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -351,22 +351,26 @@ const findTargetSumWays = (nums, target) => {
		};
		```

	TypeScript:

	```typescript
	TypeScript:

	```ts
		function findTargetSumWays(nums: number[], target: number): number {
	const sum: number = nums.reduce((pre, cur) => pre + cur);
	if (Math.abs(target) > sum) return 0;
	if ((target + sum) % 2 === 1) return 0;
	const bagSize: number = (target + sum) / 2;
	const dp: number[] = new Array(bagSize + 1).fill(0);
	dp[0] = 1;
	for (let i = 0; i < nums.length; i++) {
	for (let j = bagSize; j >= nums[i]; j--) {
	// 把数组分成两个组合left, right.left + right = sum, left - right = target.
	const sum: number = nums.reduce((a: number, b: number): number => a + b);
	if ((sum + target) % 2 \|\| Math.abs(target) > sum) return 0;
	const left: number = (sum + target) / 2;

	// 将问题转化为装满容量为left的背包有多少种方法
	// dp[i]表示装满容量为i的背包有多少种方法
	const dp: number[] = new Array(left + 1).fill(0);
	dp[0] = 1; // 装满容量为0的背包有1种方法(什么也不装)
	for (let i: number = 0; i < nums.length; i++) {
	for (let j: number = left; j >= nums[i]; j--) {
		dp[j] += dp[j - nums[i]];
		}
		}
	return dp[bagSize];
	return dp[left];
		};
		```

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27 changes: 15 additions & 12 deletions problems/1049.最后一块石头的重量II.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -277,26 +277,29 @@ var lastStoneWeightII = function (stones) {
		};
		```

	TypeScript:

	```typescript
	TypeScript版本

	```ts
		function lastStoneWeightII(stones: number[]): number {
	const sum: number = stones.reduce((pre, cur) => pre + cur);
	const bagSize: number = Math.floor(sum / 2);
	const weightArr: number[] = stones;
	const valueArr: number[] = stones;
	const goodsNum: number = weightArr.length;
	const dp: number[] = new Array(bagSize + 1).fill(0);
	for (let i = 0; i < goodsNum; i++) {
	for (let j = bagSize; j >= weightArr[i]; j--) {
	dp[j] = Math.max(dp[j], dp[j - weightArr[i]] + valueArr[i]);
	const sum: number = stones.reduce((a: number, b:number): number => a + b);
	const target: number = Math.floor(sum / 2);
	const n: number = stones.length;
	// dp[j]表示容量(总数和)为j的背包所能装下的数(下标[0, i]之间任意取)的总和(<= 容量)的最大值
	const dp: number[] = new Array(target + 1).fill(0);
	for (let i: number = 0; i < n; i++ ) {
	for (let j: number = target; j >= stones[i]; j--) {
	dp[j] = Math.max(dp[j], dp[j - stones[i]] + stones[i]);
		}
		}
	return sum - dp[bagSize] * 2;
	return sum - dp[target] - dp[target];
		};
		```






		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

40 changes: 40 additions & 0 deletions problems/1365.有多少小于当前数字的数字.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -217,6 +217,46 @@ var smallerNumbersThanCurrent = function(nums) {
		};
		```

	TypeScript:

	> 暴力法:

	```typescript
	function smallerNumbersThanCurrent(nums: number[]): number[] {
	const length: number = nums.length;
	const resArr: number[] = [];
	for (let i = 0; i < length; i++) {
	let count: number = 0;
	for (let j = 0; j < length; j++) {
	if (nums[j] < nums[i]) {
	count++;
	}
	}
	resArr[i] = count;
	}
	return resArr;
	};
	```

	> 排序+hash

	```typescript
	function smallerNumbersThanCurrent(nums: number[]): number[] {
	const length: number = nums.length;
	const sortedArr: number[] = [...nums];
	sortedArr.sort((a, b) => a - b);
	const hashMap: Map<number, number> = new Map();
	for (let i = length - 1; i >= 0; i--) {
	hashMap.set(sortedArr[i], i);
	}
	const resArr: number[] = [];
	for (let i = 0; i < length; i++) {
	resArr[i] = hashMap.get(nums[i]);
	}
	return resArr;
	};
	```



		-----------------------
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