java 练习递归..计算负值

Posted 2021-05-08

import java.io.*;
import java.util.*;


// Recursion practice
class Solution {
  class Node {
   int value;
   Node next;
    
   Node(int value, Node next){
     this.value = value;
     this.next = next;
   }
    
   public void print(){
     System.out.print(this.value + ",");
     if(this.next != null) {
       this.next.print();
     }
   }
  }
  public static void main(String[] args) {
    Solution solution = new Solution();
    int[][] input = {
      {-1,2,-41,4,-8},
      {1,3,-9,121,31},
      {1,1,1}
    };
    
    for(int i=0; i< input.length; i++){
      Node root = solution.createList(input[i]);
      System.out.print("Input :");
      root.print();
      System.out.print(" ResultI: " + solution.countNeg(root));
      System.out.print(", ResultR: " + solution.countNegR(root));
      System.out.print(", ResultRH: " + solution.countNegRH(root));
      System.out.println();
    }
  }
  
  
  public Node createList(int[] input){
     Node root = null;
     for(int i=input.length-1;i>=0;i--){
        Node newNode = new Node(input[i], root);
        newNode.next = root;
        root = newNode;
     }
     return root;
   }
  
  public int countNeg(Node root){
    Node runner = root;
    int count = 0;
    while(runner != null) {
      if(runner.value < 0){
        count++;
      }
      runner = runner.next;
    }
    return count;
  }
  
  public int countNegR(Node root) {
    if(root == null){
      return 0; 
    }
    int current = 0;
    if(root.value < 0){
      current = 1;
    }
    return current + countNeg(root.next);
  }
  
  public int countNegRH(Node root) {
    if(root == null){
      return 0; 
    }
    int count = countNeg(root.next);
    if(root.value < 0){
      count += 1;
    }
    return count;
  }
   
  
}