자바 일기 2018-06-06

//37.  
    public static String Serialize(TreeNode root){
        if(root==null) return "#";
        return root.val+" "+Serialize(root.left) + " " + Serialize(root.right);
    }
    
    
    /**
     *  
     */
    private int index;
    public TreeNode Deserialize(String str) {
        if(str == null || str.trim().length() == 0)
            return null;
        String[] nums = str.split(",");
        index = 0;
        return Deserialize(nums);
    }

    public TreeNode Deserialize(String[] nums) {
        if(nums[index].equals("$")) {
            ++index;
            return null;
        }
        TreeNode node = new TreeNode(Integer.valueOf(nums[index++]));
        node.left = Deserialize(nums);
        node.right = Deserialize(nums);
        return node;
    }

// 38.  
    public static void Permutation(StringBuffer stb) {
        if (stb == null)
            return;
        // for(int i=0;i end)
            return;
        if (start == end) {
            System.out.println(stb);
        } else {
            for (int i = start; i <= end; i++) {
                // （ for i ）
                swap(stb, start, i);
                 // ，
                PermuCore(stb, start + 1, end);
                 // 
                swap(stb, start, i);
            }
        }

    }

    public static void swap(StringBuffer stb, int i, int j) {
        char temp = stb.charAt(i);
        stb.setCharAt(i, stb.charAt(j));
        stb.setCharAt(j, temp);

    }

public class moreThanHalfNum {
    public static int find(int[] arr) {
        if(arr.length<1) return -1;
        int res=arr[0];
        int count=1;
        for(int i=1;i arr.length / 2 ? res : 0;
        
    }

//40.   K  
    public static int littk(int[] arr,int k) {
        if(arr==null) return -1;
        int index=0;
        index = partion(arr,0,arr.length-1);
        int start = 0;
        int end = arr.length - 1;
        while(index!=k-1) {
            if(index>k-1){
                //end start ， 
                end = index-1;
                index=partion(arr,start,end);
            }else{
                start = index+1;
                index=partion(arr,start,end);
            }
        }
        return index;
    }
    public static int partion(int[] arr,int start,int end){
        int res = arr[start];
        while(start=res) {
                end--;
            }
            arr[start] = arr[end];
            while(startright) return;
        
        int i= partion2(arr,left,right);
        sort_fast(arr,left,i-1);
        sort_fast(arr,i+1,right);
        
    }