蓝桥杯大纲大题通用样题“Luhn算法”

清疚 2021-10-19 01:46 159阅读 0赞

**Luhn算法**

![988978-20180125142201944-1489434833.png][]

import java.util.Scanner;
    
    class BigNum{
        
        int []num;  //位数
         
        public BigNum(){
            num = new int[21];
            for(int i = 0; i < num.length; i++) {
                num[i] = 0;
            }
        }
        
        public BigNum(int n) {
            num = new int[n];
        }
        public boolean full() {
            for(int i = 0; i < num.length; i++) {
                if(num[i] != 9) {
                    return false;
                }
            }
            return true;
        }
         
        public void plusOne() {
            int tag = 0;    //从最后一位开始加，如果其9，将其变为0，另高一位加一，
                            //如果高一位是9，其变为0，高一位加一一次类推直到全为9
                            //tag == 0说明从第0位开始
            if(num[tag]!=9) {
                num[tag]++;
                return;
            }else {
                if(full())  return; //如果全为9则溢出
                 
                //关键算法。。进位操作
                while(true) {
                    num[tag]=0;
                    tag++;
                    if(num[tag] != 9) {
                        num[tag]++;
                        return;
                    }
                }
            }
        }
        public void show() {
            for(int i = num.length-1; i >-1; i--) {
                System.out.print(num[i]);
            }
            System.out.println();
        }
        
        
        
        public void setElem(int pos, int n) {
            num[pos] = n;
        }
         
        public boolean isLuhn() {
            int OddPlus=0;  //奇数位和，在数组中为偶数位和
            int EvenPlus=0; //偶数位和，在数组中为奇数位和
            
            for(int i = 0; i < num.length; i+=2) {
                OddPlus+=num[i];
            }
            
            int num2=-999;
            for(int i = 1; i < num.length; i+=2) {
                num2 = num[i]*2;
                if (num2>9) {
                    num2-=9;
                }
                EvenPlus+=num2;
            }
            OddPlus+=EvenPlus;
            if (OddPlus%10==0) {
                return true;
            }
            return false;
        }
    }
    
    
    public class ComformCreditCard {
    
        public static void main(String[] args) {
            // TODO Auto-generated method stub
            Scanner scanner = new Scanner(System.in);
            
            //输入字符串
            String str = scanner.next();
            //从字符串提取数字
            BigNum bNum = new BigNum(str.length());
            
            
            
            //放入数据
            for (int j = 0; j < str.length(); j++) {
                bNum.setElem(j, str.charAt(j)-48);
            }
            
            if (bNum.isLuhn()) {
                System.out.print("成功");
            }else {
                System.out.print("失败");
            }
            
            
            
            
        }
    
    }

转载于:https://www.cnblogs.com/jzl123/p/8351054.html

[988978-20180125142201944-1489434833.png]: /images/20211018/deee39e4ae7d4a5eb21c0659b6a77205.png