AcWing 792. 高精度减法（Java）    原题链接    简单

作者： 作者的头像   云浪行川 ,  2020-09-23 00:19:06 ,  所有人可见 ,  阅读 513

1


踩的坑

判断前导0的情况一波三折
ArrayList 的subList(start，end) 的方法
返回的是数组中的[start,end)区间
其次返回的类型是List 不是ArrayList 怎么还有这么不智能的情况

最后就是记得保留1位
忘了答案是0的情况，导致我过了12点才调通。。。。

Java代码

import java.util.*;

public class Main{
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String a = scanner.next(); 
        String b = scanner.next();

        ArrayList<Integer> aa = new ArrayList<Integer>();
        ArrayList<Integer> bb = new ArrayList<Integer>();

        for (int i = a.length() - 1; i >= 0; i--){
            aa.add(a.charAt(i) - '0');
        }
        for (int j = b.length() - 1; j >= 0; j-- ){
            bb.add(b.charAt(j) - '0');
        }
        if (cmp(aa,bb)){
            List<Integer> c = sub(aa,bb);
            for(int k = c.size() - 1; k >= 0 ; k--){
            System.out.print(c.get(k));
            } 

        }
        else {
            System.out.print('-');
            List<Integer> c = sub(bb,aa);
            for(int k = c.size() - 1; k >= 0 ; k--){
            System.out.print(c.get(k));
            } 
        }
    }
    public static boolean cmp(ArrayList<Integer> aa, ArrayList<Integer> bb){
        if(aa.size() != bb.size()){
            return aa.size() > bb.size();
        }
        else{
            for(int i = aa.size() - 1; i >= 0; i--){
                if(aa.get(i) != bb.get(i)){
                    return aa.get(i) > bb.get(i);
                }
            }
        }
        return true;
    }

    public static List<Integer> sub(ArrayList<Integer> aa,ArrayList<Integer> bb){
        ArrayList<Integer> c = new ArrayList<Integer>();

        for(int i = 0, t = 0; i < aa.size(); i++){

            t = aa.get(i) - t;

            if ( i < bb.size()) t -= bb.get(i);

            c.add((t + 10) % 10);
            if ( t < 0) t = 1;
            else t = 0;
        }
        int i = 0;

        while(i < c.size() - 1){
            if(c.get(i) == 0){
               i++;
            }
            else break;
        }

        return c.subList(i, c.size());
    }
}

4 评论

用户头像
付有杰   2022-04-06 23:45         踩      回复

给你看看我的版本

package acwing.base.bindarysearch.高精度减法;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        char[] a = reader.readLine().toCharArray();
        char[] b = reader.readLine().toCharArray();
        boolean aBiggerThanB = isABiggerThanB(a, b);
        String result = aBiggerThanB ? subBigNum(a, b) : "-" + subBigNum(b, a);
        System.out.println(result);
    }
    private static boolean isABiggerThanB(String a,String b){
        return isABiggerThanB(a.toCharArray(),b.toCharArray());
    }

    private static boolean isABiggerThanB(final char[] a, final char[] b) {
        int aLen = a.length;
        int bLen = b.length;
        if (aLen > bLen) {
            return true;
        }
        if (aLen < bLen) {
            return false;
        }
        int index = 0;
        while (index < aLen) {
            if (a[index] < b[index]) {
                return false;
            }
            if (a[index] > b[index]) {
                return true;
            }
            index++;
        }
        return true;
    }
    private static String subBigNum(String a, String b) {
        return subBigNum(a.toCharArray(), b.toCharArray());
    }

    private static String subBigNum(final char[] a, final char[] b) {
        int c = 0;
        int i = a.length-1;
        int j = b.length-1;
        LinkedList<Integer> deque = new LinkedList<>();
        while (i >= 0 || j >= 0 || c > 0) {
            int aNum = i >= 0? a[i] - '0' : 0;
            int bNum = j >= 0? b[j] - '0' : 0;
            aNum -= c;
            int sum = aNum - bNum;
            if (sum < 0) {
                sum += 10;
                c = 1;
            }else {
                c = 0;
            }
            deque.addFirst(sum);
            i--;
            j--;

        }
        while (deque.size() > 1 && deque.getFirst() == 0){
            deque.removeFirst();
        }
        return deque.stream().map(String::valueOf).reduce("", (a1, a2) -> a1 + a2);
    }
}
用户头像
wr_2   2022-03-18 23:11         踩      回复 
 while (C.size() > 1 && C.get(C.size() - 1) == 0) {
            C.remove(C.size() - 1);
        }
        return C;
用户头像
鼠人师师   2022-05-15 00:56         踩      回复

和我一样

用户头像
crayon不小心   2021-01-27 19:54         踩      回复 
import java.math.BigInteger;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        BigInteger a = sc.nextBigInteger();
        BigInteger b = sc.nextBigInteger();
        BigInteger cnt = a.subtract(b);
        System.out.println(cnt);
    }
}

JAVA大整形类，方便快捷。