alg4 1.2.16 实现一个简易的 分数 计算工具类

Rational.java

package life.yanfeng.study.algorithm;

import edu.princeton.cs.algs4.StdOut;

// for 1.2.16
public class Rational {
    // 分子.
    private long numerator;

    // 计算最大公约数. ref: https://zh.wikipedia.org/wiki/%E8%BC%BE%E8%BD%89%E7%9B%B8%E9%99%A4%E6%B3%95
    private static long gcd(long a, long b) {
        if (b == 0) {
            return a;
        } else {
            return gcd(b, a % b);
        }
    }

    // 分母.
    private long denominator;

    public long numerator() {
        return this.numerator;
    }

    public long denominator() {
        return this.denominator;
    }

    Rational(long numerator, long denominator) {
        assert numerator > Integer.MIN_VALUE && numerator < Integer.MAX_VALUE &&
                denominator > Integer.MIN_VALUE && denominator < Integer.MAX_VALUE &&
                numerator * denominator > Integer.MIN_VALUE && numerator * denominator < Integer.MAX_VALUE
                : "numerator or denominator is overflow";

        long gcdNumber = gcd(Math.abs(numerator), Math.abs(denominator));

        if (gcdNumber > 1) { // 保证没有公因子.
            numerator /= gcdNumber;
            denominator /= gcdNumber;
        }

        if (numerator * denominator < 0) {
            numerator = -Math.abs(numerator);
        } else {
            numerator = Math.abs(numerator);
        }
        denominator = Math.abs(denominator);

        this.numerator = numerator;
        this.denominator = denominator;
    }

    public Rational plus(Rational b) {
        return new Rational(this.numerator() * b.denominator() + b.numerator() * this.denominator(),
                this.denominator() * b.denominator());
    }

    public Rational minus(Rational b) {
        return plus(new Rational(-b.numerator(), b.denominator()));
    }

    public Rational times(Rational b) {
        return new Rational(this.numerator() * b.numerator(),
                this.denominator() * b.denominator());
    }

    public Rational divides(Rational b) {
        return times(new Rational(b.denominator(), b.numerator()));
    }

    public boolean equals(Rational b) {
        return this.numerator() == b.numerator() && this.denominator == b.denominator();
    }

    public String toString() {
        return this.numerator() + "/" + this.denominator();
    }

    public static void main(String[] args) {
        Rational a = new Rational(1, 3);
        Rational b = new Rational(2, 3);

        StdOut.println(a.plus(b).equals(new Rational(1, 1)));
        StdOut.println(a.minus(b).equals(new Rational(-1, 3)));
        StdOut.println(a.times(b).equals(new Rational(2, 9)));
        StdOut.println(a.divides(b).equals(new Rational(1, 2)));

        StdOut.println(a.times(b).toString());
    }
}

所以说, 不用羡慕 直接支持 分数计算的 编程语言.
在特定业务场景下, 完全可以自己实现 基于 分数的 较精确的 数学计算.