Commit 8824e11

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20200912

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	`1`	`+/*`
	`2`	`+ * @lc app=leetcode id=199 lang=java`
	`3`	`+ *`
	`4`	`+ * [199] Binary Tree Right Side View`
	`5`	`+ */`
	`6`	`+`
	`7`	`+// @lc code=start`
	`8`	`+/**`
	`9`	`+ * Definition for a binary tree node.`
	`10`	`+ * public class TreeNode {`
	`11`	`+ * int val;`
	`12`	`+ * TreeNode left;`
	`13`	`+ * TreeNode right;`
	`14`	`+ * TreeNode() {}`
	`15`	`+ * TreeNode(int val) { this.val = val; }`
	`16`	`+ * TreeNode(int val, TreeNode left, TreeNode right) {`
	`17`	`+ * this.val = val;`
	`18`	`+ * this.left = left;`
	`19`	`+ * this.right = right;`
	`20`	`+ * }`
	`21`	`+ * }`
	`22`	`+ */`
	`23`	`+class Solution {`
	`24`	`+ /*`
	`25`	`+ 类似preorder, 但是仅当level = res.size()时,之前level都加上了目标node,此时加上的root就是right view的第一个`
	`26`	`+ 之后每次先向右边递归就能得到每层的right view`
	`27`	`+ time: O(h)`
	`28`	`+ space: O(h)`
	`29`	`+ */`
	`30`	`+ public List<Integer> rightSideView(TreeNode root) {`
	`31`	`+ List<Integer> res = new ArrayList<>();`
	`32`	`+ if (root == null) return res;`
	`33`	`+ rightView(root, res, 0);`
	`34`	`+ return res;`
	`35`	`+ }`
	`36`	`+`
	`37`	`+ private void rightView(TreeNode root, List<Integer> res, int level) {`
	`38`	`+ if (root == null) return;`
	`39`	`+ if (level == res.size()) res.add(root.val);`
	`40`	`+ rightView(root.right, res, level + 1);`
	`41`	`+ rightView(root.left, res, level + 1);`
	`42`	`+ }`
	`43`	`+}`
	`44`	`+// @lc code=end`
	`45`	`+`

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	`1`	`+/*`
	`2`	`+ * @lc app=leetcode id=216 lang=java`
	`3`	`+ *`
	`4`	`+ * [216] Combination Sum III`
	`5`	`+ */`
	`6`	`+`
	`7`	`+// @lc code=start`
	`8`	`+class Solution {`
	`9`	`+ /*`
	`10`	`+ dfs`
	`11`	`+ time: O(n*2^n) n = 9`
	`12`	`+ sapce: O(n)`
	`13`	`+ */`
	`14`	`+ public List<List<Integer>> combinationSum3(int k, int n) {`
	`15`	`+ List<List<Integer>> res = new ArrayList<>();`
	`16`	`+ dfs(res, new ArrayList<>(), k, n, 1);`
	`17`	`+ return res;`
	`18`	`+ }`
	`19`	`+`
	`20`	`+ private void dfs(List<List<Integer>> res, List<Integer> cur, int k, int n, int pos) {`
	`21`	`+ if (n <= 0 \|\| cur.size() == k) {`
	`22`	`+ if (cur.size() == k && n == 0) {`
	`23`	`+ res.add(new ArrayList<>(cur));`
	`24`	`+ }`
	`25`	`+ return;`
	`26`	`+ }`
	`27`	`+ for (int i = pos; i <= 9; ++i) {`
	`28`	`+ cur.add(i);`
	`29`	`+ dfs(res, cur, k, n - i, i + 1);`
	`30`	`+ cur.remove(cur.size() - 1);`
	`31`	`+ }`
	`32`	`+ }`
	`33`	`+}`
	`34`	`+// @lc code=end`
	`35`	`+`

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`163`	`163`	`## Tree`
`164`	`164`	`\| Problem \| Solution`
`165`	`165`	`:- \| :-:`
	`166`	`+[199. Binary Tree Right Side View](https://leetcode.com/problems/binary-tree-right-side-view/) \| [preorder + level check](https://github.com/Yukinichi/leetcode/blob/master/Java/199.binary-tree-right-side-view.java)`
`166`	`167`	`[662. Maximum Width of Binary Tree](https://leetcode.com/problems/maximum-width-of-binary-tree/) \| [Solution](https://github.com/Yukinichi/leetcode/blob/master/Java/662.maximum-width-of-binary-tree.java)`
`167`	`168`	`[1110. Delete Nodes And Return Forest](https://leetcode.com/problems/delete-nodes-and-return-forest/) \| [Solution](https://github.com/Yukinichi/leetcode/blob/master/Java/1110.delete-nodes-and-return-forest.java)`
`168`	`169`

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