跳阶梯

Author: wb-hjk570755

src/com/blankj/concurrent/BoundedQueue.java

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+package com.blankj.concurrent;
+
+/**
+ * Description:
+ * Copyright: Copyright (c) 2012
+ * Company: keruyun Technology(Beijing) Chengdu Co. Ltd.
+ *
+ * @author huangjk
+ * @version 1.0 2020/9/22
+ */
+public class BoundedQueue {
+}

src/com/blankj/myself/InorderTraversal.java

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+package com.blankj.myself;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Description:
+ * Copyright: Copyright (c) 2012
+ * Company: keruyun Technology(Beijing) Chengdu Co. Ltd.
+ *
+ * @author huangjk
+ * @version 1.0 2020/9/14
+ */
+public class InorderTraversal {
+    public static void main(String[] args) {
+
+    }
+
+
+    public List<Integer> inorderTraversal(TreeNode root) {
+        List<Integer> list = new ArrayList<>();
+        dfs(root,list);
+        return list;
+    }
+
+    public void dfs(TreeNode root,List<Integer> list) {
+        if(root==null){
+            return;
+        }
+        dfs(root.left,list);
+        list.add(root.val);
+        dfs(root.right,list);
+    }
+
+
+
+    public class TreeNode {
+      int val;
+      TreeNode left;
+      TreeNode right;
+      TreeNode(int x) { val = x; }
+    }
+}

src/com/blankj/myself/InorderTraversalByStack.java

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+package com.blankj.myself;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Stack;
+
+import com.blankj.myself.InorderTraversal.TreeNode;
+
+/**
+ * Description:
+ * Copyright: Copyright (c) 2012
+ * Company: keruyun Technology(Beijing) Chengdu Co. Ltd.
+ *
+ * @author huangjk
+ * @version 1.0 2020/9/14
+ */
+public class InorderTraversalByStack {
+
+    public List<Integer> inorderTraversal(TreeNode root) {
+        List<Integer> list = new ArrayList<>();
+        Stack stack = new Stack();
+        TreeNode curr = root;
+        while (curr!=null||!stack.isEmpty()){
+            if(curr!=null){
+                stack.push(curr.left);
+                curr = curr.left;
+            }else {
+                curr = (TreeNode) stack.pop();
+                list.add(curr.val);
+                curr = curr.right;
+            }
+        }
+        return list;
+    }
+}

src/com/blankj/myself/IsPalindrome.java

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+package com.blankj.myself;
+
+/**
+ * Description:
+ * Copyright: Copyright (c) 2012
+ * Company: keruyun Technology(Beijing) Chengdu Co. Ltd.
+ *
+ * @author huangjk
+ * @version 1.0 2020/9/21
+ */
+public class IsPalindrome {
+    public static void main(String[] args) {
+        IsPalindrome isPalindrome = new IsPalindrome();
+        System.out.println(isPalindrome.isPalindrome(1001));
+    }
+    public boolean isPalindrome(int x) {
+        boolean isPalindrome = true;
+        String xStr = String.valueOf(x);
+
+        for (int i=0;i<xStr.length()/2;i++){
+            if(xStr.charAt(i)!=xStr.charAt(xStr.length()-i-1)){
+                isPalindrome = false;
+            }
+        }
+        return isPalindrome;
+    }
+}

src/com/blankj/myself/LongestCommonPrefix.java

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+package com.blankj.myself;
+
+/**
+ * Description:
+ * Copyright: Copyright (c) 2012
+ * Company: keruyun Technology(Beijing) Chengdu Co. Ltd.
+ *
+ * @author huangjk
+ * @version 1.0 2020/9/22
+ */
+public class LongestCommonPrefix {
+
+    public String longestCommonPrefix(String[] strs) {
+        String result = new String();
+        String first = strs[0];
+        if(first==null){
+            return "";
+        }
+        for(int j=0;j<first.length();j++){
+            boolean end = false;
+            char b = first.charAt(j);
+            for(int i=1;i<strs.length;i++){
+                String a = strs[i];
+                if(first.charAt(i)!=b){
+                    end = true;
+                    break;
+                }
+            }
+            result = result+b;
+            if(end==true){
+                break;
+            }
+        }
+        return result;
+    }
+}

src/com/blankj/myself/RebuildTree.java

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+package com.blankj.myself;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Description:
+ * Copyright: Copyright (c) 2012
+ * Company: keruyun Technology(Beijing) Chengdu Co. Ltd.
+ *
+ * @author huangjk
+ * @version 1.0 2020/9/16
+ */
+public class RebuildTree {
+    
+
+    public TreeNode buildTree(int[] preorder, int[] inorder) {
+       Map indexMap = new HashMap<Integer,Integer>();
+        for (int i = 0; i < preorder.length; i++) {
+            indexMap.put(inorder[i],i);
+        }
+        return reBuildTree(0,0,inorder.length-1,preorder,inorder,indexMap);
+    }
+
+
+    public TreeNode reBuildTree(int preRootIndex, int inorderLeftIndex,int inorderRightIndex,int[] preorder, int[] inorder,Map indexMap) {
+        if(inorderLeftIndex>=inorderRightIndex){
+            return null;
+        }
+        int index = (int)indexMap.get(preorder[preRootIndex]);
+        TreeNode treeNode = new TreeNode(preorder[preRootIndex]);
+        treeNode.left = reBuildTree(preRootIndex+1,inorderLeftIndex,index-1,preorder,inorder,indexMap);
+        treeNode.right = reBuildTree(preRootIndex+index-inorderLeftIndex+1,index+1,inorderRightIndex,preorder,inorder,indexMap);
+        return treeNode;
+    }
+
+
+
+    public class TreeNode {
+      int val;
+      TreeNode left;
+      TreeNode right;
+      TreeNode(int x) { val = x; }
+  }
+}

src/com/blankj/myself/RomanToInt.java

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+package com.blankj.myself;
+
+/**
+ * Description:
+ * Copyright: Copyright (c) 2012
+ * Company: keruyun Technology(Beijing) Chengdu Co. Ltd.
+ *
+ * @author huangjk
+ * @version 1.0 2020/9/21
+ */
+public class RomanToInt {
+    public int romanToInt(String s) {
+        int sum = 0;
+        int pre = cast(s.charAt(0));
+        for(int i=1;i<s.length();i++){
+            int cuur = cast(s.charAt(i));
+            if(pre<cuur){
+                sum = sum -pre;
+            }else {
+                sum = sum +pre;
+            }
+            pre = cuur;
+        }
+        sum = sum + cast(s.charAt(s.length()-1));
+        return sum;
+    }
+
+    private int cast(char i){
+        switch (i){
+            case('I'):return 1;
+            case('V'):return 5;
+            case('X'):return 10;
+            case('L'):return 50;
+            case('C'):return 100;
+            case('D'):return 500;
+            case('M'):return 1000;
+            default:return 0;
+        }
+
+    }
+}

src/com/blankj/myself/Test.java

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+package com.blankj.myself;
+
+/**
+ * Description:
+ * Copyright: Copyright (c) 2012
+ * Company: keruyun Technology(Beijing) Chengdu Co. Ltd.
+ *
+ * @author huangjk
+ * @version 1.0 2020/9/10
+ */
+public class Test {
+    public static void main(String[] args) {
+        Test a = new Test();
+    }
+}

src/com/blankj/myself/ThreeSum.java

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+package com.blankj.myself;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Description:
+ * Copyright: Copyright (c) 2012
+ * Company: keruyun Technology(Beijing) Chengdu Co. Ltd.
+ *
+ * @author huangjk
+ * @version 1.0 2020/9/21
+ */
+public class ThreeSum {
+    public List<List<Integer>> threeSum(int[] nums) {
+        List<List<Integer>> result = new ArrayList<>();
+        Arrays.sort(nums);
+        int length = nums.length;
+        for(int k=0;k<length-2;k++){
+            if(nums[k]>0){
+                return result;
+            }
+            if(k>0&&nums[k]==nums[k-1]){
+                continue;
+            }
+            int L=k+1;
+            int R=length-1;
+            while (L<R){
+                int sum = nums[k] + nums[L] + nums[R];
+                if(sum==0){
+                    result.add(Arrays.asList(nums[k] , nums[L] , nums[R]));
+                    while (L<R &&nums[L]==nums[L+1]){
+                        L = L+1;
+                    }
+                    while (L<R &&nums[R]==nums[R-1]){
+                        R = R-1;
+                    }
+                    L = L+1;
+                    R = R-1;
+                }
+                if(sum < 0){
+                    L = L+1;
+                }
+                if(sum > 0){
+                    R = R-1;
+                }
+            }
+        }
+        return result;
+    }
+}