Commit f6df74a

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20190315

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Lines changed: 39 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,39 @@`
	`1`	`+package code;`
	`2`	`+`
	`3`	`+import java.util.ArrayList;`
	`4`	`+import java.util.List;`
	`5`	`+/*`
	`6`	`+ * 113. Path Sum II`
	`7`	`+ * 题意:找从root到叶子节点和为sum的路径`
	`8`	`+ * 难度:Medium`
	`9`	`+ * 分类:Tree, Depth-first Search`
	`10`	`+ * 思路:回溯,注意因为节点上可能正值,可能负值,所以不能剪枝`
	`11`	`+ * Tips:`
	`12`	`+ */`
	`13`	`+public class lc113 {`
	`14`	`+ public class TreeNode {`
	`15`	`+ int val;`
	`16`	`+ TreeNode left;`
	`17`	`+ TreeNode right;`
	`18`	`+ TreeNode(int x) {`
	`19`	`+ val = x;`
	`20`	`+ }`
	`21`	`+ }`
	`22`	`+ public List<List<Integer>> pathSum(TreeNode root, int sum) {`
	`23`	`+ List<List<Integer>> res = new ArrayList<>();`
	`24`	`+ helper(res, root, sum, 0, new ArrayList<>());`
	`25`	`+ return res;`
	`26`	`+ }`
	`27`	`+ public void helper(List<List<Integer>> res, TreeNode root, int sum, int curr, List<Integer> curr_ls) {`
	`28`	`+ if(root==null) return;`
	`29`	`+ curr_ls.add(root.val);`
	`30`	`+ if(curr+root.val==sum && root.left==null && root.right==null) { //到叶子节点`
	`31`	`+ res.add(new ArrayList<>(curr_ls));`
	`32`	`+ curr_ls.remove(curr_ls.size()-1);`
	`33`	`+ return;`
	`34`	`+ }`
	`35`	`+ helper(res, root.left, sum, curr+root.val, curr_ls);`
	`36`	`+ helper(res, root.right, sum, curr+root.val, curr_ls);`
	`37`	`+ curr_ls.remove(curr_ls.size()-1);`
	`38`	`+ }`
	`39`	`+}`

Lines changed: 1 addition & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -28,7 +28,7 @@ public static void nextPermutation(int[] nums) {`
`28`	`28`	`//从这个数之后的数中找出第一个比x大的数`
`29`	`29`	`int n = nums[ptr];`
`30`	`30`	`int ptr2 = ptr;`
`31`		`- for(int i=ptr+1; i<nums.length; i++){`
	`31`	`+ for(int i=ptr+1; i<nums.length; i++){//这不用这么麻烦,后边的数有序的,这可以简化`
`32`	`32`	`if( nums[i]>nums[ptr-1] && nums[i]<=n ) {//注意 <= {2,3,1,3,3}`
`33`	`33`	`n = nums[i];`
`34`	`34`	`ptr2 = i;`

Lines changed: 1 addition & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -14,7 +14,7 @@ public List<List<String>> groupAnagrams(String[] strs) {`
`14`	`14`	`HashMap<String,List<String>> m = new HashMap();`
`15`	`15`	`for (int i = 0; i < strs.length ; i++) {`
`16`	`16`	`char[] chs = strs[i].toCharArray();`
`17`		`- Arrays.sort(chs);`
	`17`	`+ Arrays.sort(chs);//对字符串排序`
`18`	`18`	`String key = String.valueOf(chs);`
`19`	`19`	`if(m.containsKey(key))`
`20`	`20`	`m.get(key).add(strs[i]);`

Lines changed: 3 additions & 0 deletions

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