高精度加减乘除

高精度加减乘除

非API手写大数据高精度加减乘除

加法：

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String a = sc.nextLine();
        String b = sc.nextLine();
        int n = a.length();
        int m = b.length();
        int[] numA = new int[n];
        int[] numB = new int[m];
        for(int i = n - 1; i >= 0; --i) {
            numA[n - i - 1] = a.charAt(i) - '0';
        }
        for(int i = m - 1; i >= 0; --i) {
            numB[m - i - 1] = b.charAt(i) - '0';
        }
        
        int[] sum = add(numA, numB);
        for(int i = sum.length - 1; i >= 0; --i) {
            if(i == sum.length - 1 && sum[i] == 0) continue;
            System.out.print(sum[i]);
        }
    }
    
    public static int[] add(int[] numA, int[] numB) {
        int n = numA.length, m = numB.length;
        int[] res = new int[Math.max(n, m) + 1];
        int carry = 0;
        for(int i = 0; i < n || i < m; ++i) {
            if(i < n) carry += numA[i];
            if(i < m) carry += numB[i];
            res[i] = carry % 10;
            carry /= 10;
        }
        if(carry != 0) {
            res[Math.max(n, m)] = carry;
        }
        return res;
    }
}

减法：

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String a = sc.nextLine();
        String b = sc.nextLine();
        int n = a.length();
        int m = b.length();
        int[] numA = new int[n];
        int[] numB = new int[m];
        for(int i = n - 1; i >= 0; --i) {
            numA[n - i - 1] = a.charAt(i) - '0';
        }
        for(int i = m - 1; i >= 0; --i) {
            numB[m - i - 1] = b.charAt(i) - '0';
        }
        int[] res = new int[0];
        if(compare(numA, numB)) {
            res = sub(numA, numB);
        } else {
            res = sub(numB, numA);
            System.out.print("-");
        }
        boolean flag = true;
        for(int i = res.length - 1; i >= 0; --i) {
            if(i >= 1 && res[i] == 0 && flag) {
                continue;
            } else {
                flag = false;
            }
            System.out.print(res[i]);
        }
    }
    
    public static int[] sub(int[] numA, int[] numB) {
        int n = numA.length;
        int[] res = new int[n];
        int t = 0;
        for(int i = 0; i < n; ++i) {
            t = numA[i] - t;
            if(i < numB.length) {
                t -= numB[i];
            }
            res[i] = (t + 10) % 10;
            if(t >= 0) t = 0;
            else t = 1;
        }
        return res;
    }
    
    public static boolean compare(int[] a, int[] b) {
        if(a.length != b.length) return a.length > b.length;
        for(int i = a.length - 1; i >= 0; --i) {
            if(a[i] != b[i]) return a[i] > b[i];
        }
        return true;
    }
}

乘法：

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String a = sc.nextLine();
        int num2 = sc.nextInt();
        List<Integer> num1 = new ArrayList<>();
        for(int i = a.length() - 1; i >= 0; --i) {
            num1.add(a.charAt(i) - '0');
        }
        List<Integer> res = mul(num1, num2);
        for(int i = res.size() - 1; i >= 0; --i) {
            System.out.print(res.get(i));
        }
    }
    
    public static List<Integer> mul(List<Integer> num1, int num2) {
        int t = 0;
        List<Integer> res = new ArrayList<>();
        for(int i = 0; i < num1.size() || t != 0; ++i) {
            if(i < num1.size()) {
                t += num1.get(i) * num2;
            }
            res.add(t % 10);
            t /= 10;
        }
        int idx = res.size() - 1;
        while(idx > 0 && res.get(idx) == 0) {
            res.remove(idx);
            idx--;
        }
        return res;
    }
}

除法：

import java.util.*;

public class Main {
    public static int r; // 余数
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String a = sc.nextLine();
        int num2 = sc.nextInt();
        List<Integer> num1 = new ArrayList<>();
        for(int i = a.length() - 1; i >= 0; --i) {
            num1.add(a.charAt(i) - '0');
        }
        List<Integer> res = div(num1, num2);
        for(int i = res.size() - 1; i >= 0; --i) {
            System.out.print(res.get(i));
        }
        System.out.printf("\n%d", r);
    }
    
    public static List<Integer> div(List<Integer> num1, int num2) {
        List<Integer> res = new ArrayList<>();
        for(int i = num1.size() - 1; i >= 0; --i) {
            r = r * 10 + num1.get(i);
            res.add(r / num2);
            r %= num2;
        }
        Collections.reverse(res);
        int idx = res.size() - 1;
        while(idx > 0 && res.get(idx) == 0) {
            res.remove(idx);
            idx--;
        }
        return res;
    }
}