package lainxi;

import java.util.Random;

public class text2 {

    static String[] equs = new String[50];   //存储算式集合的数组
    static int[] results = new int[50];  // 存储计算结果的数组

    public static void main(String[] args) {
        printHeader();  //打印说明
        generateEquations();  // 产生加减法算式，并存储在数组里
        printExercise();  //打印输出习题
        printCalculations();  //打印计算结果
    }

    public static void printHeader() {
        System.out.println("----------------------------------------------");
        System.out.println("--程序输出50道100以内的加减法算式习题---");
        System.out.println("--每次运行可得到一套习题和答案---");
        System.out.println("----------------------------------------------");
    }

    public static void generateEquations() {
        int m = 0, n = 0, value = 0;
        char o = '+';
        Random random = new Random();
        int ov = random.nextInt(2); // 0：加号； 1：减号
        for (int i = 0; i < 50; i++) {
            if(ov == 0) {
                o = '+';
                do {
                    m = random.nextInt(101);
                    n = random.nextInt(101);
                    value = m + n;
                }while(value > 100);
            }else {
                o = '-';
                do {
                    m = random.nextInt(101);
                    n = random.nextInt(101);
                    value = m - n;
                }while(value < 0);
            }
            ov = random.nextInt(2);
            equs[i] = "" + m + o + n + " = ";
            results[i] = value;
        }
    }

    public static void printExercise() {
        for(int i = 0; i < equs.length; i++) {
            System.out.println((i+1) + ":\t" + equs[i]);
        }
    }

    public static void printCalculations() {
        System.out.println("\n-----以下是习题的答案-------");
        for(int i = 0; i < results.length; i++) {
            System.out.println((i+1) + ":\t" + results[i]);
        }
    }

}