题解 | #Rational Arithmetic (20)#

题解链接

class RationalNum {
    //分子
    private long numerator;
    //分母
    private long denominator;
    //整数部分
    private long integer;
    //判断符号
    private boolean isNegative = false;
    //判断分母为零
    private boolean isZero = false;
    //参与运算的分子
    private long totalNumerator;
    //构造方法 对这些值初始化
    public RationalNum(long n, long d) {
        if(d == 0) {
            isZero = true;
            return;
        }
        if(n < 0) {
            isNegative = true;
        }
        //经过除法计算可能将分母变为负数
        if(d < 0) {
            isNegative = !isNegative;
        }
        //如果输入是假分数转换为真分数
        integer = n / d;
        numerator = n - integer * d;
        denominator = Math.abs(d);
        //化简 分子分母同时除以最大公约数
        if(numerator > 1 || numerator < -1) {
            long gcd = isGcd(Math.abs(numerator), denominator);
            if(gcd > 0) {
                numerator /= gcd;
                denominator /= gcd;
            }
        }
        //进行计算的分子,一定是简化后
        totalNumerator = integer * denominator + numerator;
    }
    //辗转相除法,求最大公约数
    private long isGcd(long a, long b) {
        if(b == 0) {
            return a;
        }
        return isGcd(b,a % b);
    }
    //根据字符串得到分子
    public static long parseNumerator(String s) {
        return Long.parseLong(s.substring(0, s.indexOf("/")));
    }
    //根据字符串得到分母
    public static long paresDenominator(String s) {
        return Long.parseLong(s.substring(s.indexOf('/')+1));
    }
    //加法操作
    public RationalNum add(RationalNum r) {
        long n = totalNumerator * r.denominator + denominator * r.totalNumerator;
        long d = denominator * r.denominator;
        return new RationalNum(n, d);
    }
    //减法操作
    public RationalNum sub(RationalNum r) {
        long n = totalNumerator * r.denominator - denominator * r.totalNumerator;
        long d = denominator * r.denominator;
        return new RationalNum(n, d);
    }
    //乘法操作
    public RationalNum mul(RationalNum r) {
        long n = totalNumerator * r.totalNumerator;
        long d = denominator * r.denominator;
        return new RationalNum(n , d);
    }
    //除法操作
    public RationalNum div(RationalNum r) {
        long n = totalNumerator * r.denominator;
        long d = denominator * r.totalNumerator;
        return new RationalNum(n , d);
    }
    //对于输出进行重写
    @Override
    public String toString() {
        StringBuffer s = new StringBuffer();
        if(isZero) {
            s.append("Inf");
            return new String(s);
        }
        if(integer == 0 && numerator == 0) {
            s.append("0");
            return new String(s);
        }
        if(isNegative) {
            s.append("(-");
        }
        //有整数,注意与分子空格
        if(integer != 0) {
            s.append(Math.abs(integer));
            if(numerator != 0) {
                s.append(' ');
            }
        }
        //可能没有整数部分
        if(numerator != 0) {
            s.append(Math.abs(numerator));
            s.append('/');
            s.append(denominator);
        }
        if(isNegative) {
            s.append(')');
        }
        return new String(s);
    }
}
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) { 
            //接收一个分数,next遇到换行空格等空白符停止,且不包含上述空白符
            String s = in.next();
            RationalNum r1 = new RationalNum(RationalNum.parseNumerator(s),RationalNum.paresDenominator(s));
           //在接收第二个分数
            s = in.next();
            RationalNum r2 = new RationalNum(RationalNum.parseNumerator(s),RationalNum.paresDenominator(s));
            System.out.println(r1 + " + " + r2 + " = " + r1.add(r2));
            System.out.println(r1 + " - " + r2 + " = " + r1.sub(r2));
            System.out.println(r1 + " * " + r2 + " = " + r1.mul(r2));
            System.out.println(r1 + " / " + r2 + " = " + r1.div(r2));
        }
    }
}