Temp

public ListNode ReverseList(ListNode head) { ListNode pre = null; ListNode cur = head; ListNode nex = null; // 这里可以指向nullptr，循环里面要重新指向 while (cur != null) { nex = cur.next; cur.next = pre; pre = cur; cur = nex; } return pre; }

public int[] MySort(int[] arr) { quickSort(arr, 0, arr.length - 1); return arr; }

private void quickSort(int[] array, int start, int end) { if (start < end) { int key = array[start];//用待排数组的第一个作为中枢 int i = start; for (int j = start + 1; j <= end; j++) { if (key > array[j]) { swap(array, j, ++i); } } array[start] = array[i];//先挪，然后再把中枢放到指定位置 array[i] = key; quickSort(array, start, i - 1); quickSort(array, i + 1, end); } }

//交换两个数的值 public void swap(int[] A, int i, int j) { if (i != j) { A[i] ^= A[j]; A[j] ^= A[i]; A[i] ^= A[j]; } }

public void preorder(TreeNode root, List list) { if (root != null) { list.add(root.val); preorder(root.left, list); preorder(root.right, list); } } public void inorder(TreeNode root, List list) { if (root != null) { inorder(root.left, list); list.add(root.val); inorder(root.right, list); } } public void postorder(TreeNode root, List list) { if (root != null) { postorder(root.left, list); postorder(root.right, list); list.add(root.val); } }

ArrayList<ArrayList> res = new ArrayList<ArrayList>(); public ArrayList<ArrayList> levelOrder (TreeNode root) { // write code here if(root == null){ return res; } count(root,0); return res; }

public void count(TreeNode node, int level){
    if(level == res.size()){
        res.add(new ArrayList<Integer>());
    }

   ArrayList<Integer> list = res.get(level);
   list.add(node.val);

   if(node.left != null){
       count(node.left, level+1);
   }

   if(node.right != null){
       count(node.right, level+1);
   }

}

public int[] twoSum (int[] numbers, int target) { int[] result = new int[2]; Map<Integer, Integer> map = new HashMap(); for(int i = 0; i < numbers.length; i++) { if(map.get(target - numbers[i]) != null) { result[0] = map.get(target - numbers[i]) + 1; result[1] = i + 1; return result; } map.put(numbers[i], i); } return result; }

public void push(int node) { stack1.push(node); }

public int pop() {
    if (stack2.size() <= 0) {
        while (stack1.size() != 0) {
            stack2.push(stack1.pop());
        }
    }
    return stack2.pop();
}

public int JumpFloor(int target) { if (target <= 1) { return 1; } // a 表示第 f[i-2] 项，b 表示第 f[i-1] 项 int a = 1, b = 1, c = 0; for (int i = 2; i <= target; i++) { c = a + b; // f[i] = f[i - 1] + f[i - 2]; // 为下一次循环求 f[i + 1] 做准备 a = b; // f[i - 2] = f[i - 1] b = c; // f[i - 1] = f[i] } return c; }

public ListNode reverseKGroup (ListNode head, int k) { if(head==null||head.next==null||k==1) return head; ListNode res = new ListNode(0); res.next = head; int length = 0; ListNode pre = res, cur = head, temp = null; while(head!=null){ length++; head = head.next; } //分段使用头插法将链表反序 for(int i=0; i<length/k; i++){ //pre作为每一小段链表的头节点，负责衔接 for(int j=1; j<k; j++){ temp = cur.next; cur.next = temp.next; //相当于头插法，注意： //temp.next = cur是错误的，temp需要连接的不是前一节点，而是子序列的头节点 temp.next = pre.next; pre.next = temp; } //每个子序列反序完成后，pre，cur需要更新至下一子序列的头部 pre = cur; cur = cur.next; } return res.next; }

public static int getLongestPalindrome(String A, int n) { // write code here char[] aa =A.toCharArray(); int max=1; boolean[][] dp = new boolean[n][n]; for(int i=0;i<n;i++){ dp[i][i] = true; } for(int i=1;i<n;i++)//i指向的是字符的最后一位 for(int j=i-1;j>=0;j–){//j指向的是字符的前部。 if(i-j==1){//当两个指针靠近时，直接判断 dp[j][i]=(aa[i]==aa[j]); if(max<i-j+1) max = i-j+1; }

           else{
               if(dp[j+1][i-1]&&aa[i]==aa[j]){
                   dp[j][i]=true;
                   if(max<i-j+1)
                       max = i-j+1;
               }
               else
                   dp[j][i]=false;
           }
       }
   return max;

}

public static String LCS1(String str1, String str2) { int maxLength = 0; int index = 0; for(int i = 0; i < str2.length(); i++){ for(int j = i+1; j <= str2.length(); j++){ if(str1.contains(str2.substring(i, j)) ){ if(maxLength < j-i){ maxLength = j-i; index = i; } } else break; } } if( maxLength == 0 ){ //没有相同的字符串 return “-1”; } return str2.substring(index,index + maxLength); }