java알고리즘

반복문을 활용한 구구단

Dec 19, 2023
반복문을 활용한 구구단
 
public static void main(String[] args) {
        System.out.println("2*1=2");
        System.out.println("2*2=4");
        System.out.println("2*3=6");
        System.out.println("2*4=8");
        System.out.println("2*5=10");
        System.out.println("2*6=12");
        System.out.println("2*7=14");
        System.out.println("2*8=16");
        System.out.println("2*9=18");
        System.out.println();
        System.out.println("3*1=3");
        System.out.println("3*2=6");
        System.out.println("3*3=9");
        System.out.println("3*4=12");
        System.out.println("3*5=15");
        System.out.println("3*6=18");
        System.out.println("3*7=21");
        System.out.println("3*8=24");
        System.out.println("3*9=27");
        System.out.println();
        System.out.println("4*1=4");
        System.out.println("4*2=8");
        System.out.println("4*3=12");
        System.out.println("4*4=16");
        System.out.println("4*5=20");
        System.out.println("4*6=24");
        System.out.println("4*7=28");
        System.out.println("4*8=32");
        System.out.println("4*9=36");
        System.out.println();
        System.out.println("5*1=5");
        System.out.println("5*2=10");
        System.out.println("5*3=15");
        System.out.println("5*4=20");
        System.out.println("5*5=25");
        System.out.println("5*6=30");
        System.out.println("5*7=35");
        System.out.println("5*8=40");
        System.out.println("5*9=45");
        System.out.println();
        System.out.println("6*1=6");
        System.out.println("6*2=12");
        System.out.println("6*3=18");
        System.out.println("6*4=24");
        System.out.println("6*5=30");
        System.out.println("6*6=36");
        System.out.println("6*7=42");
        System.out.println("6*8=48");
        System.out.println("6*9=54");
        System.out.println();
        System.out.println("7*1=7");
        System.out.println("7*2=14");
        System.out.println("7*3=21");
        System.out.println("7*4=24");
        System.out.println("7*5=35");
        System.out.println("7*6=42");
        System.out.println("7*7=48");
        System.out.println("7*8=56");
        System.out.println("7*9=63");
        System.out.println();
        System.out.println("8*1=8");
        System.out.println("8*2=16");
        System.out.println("8*3=24");
        System.out.println("8*4=32");
        System.out.println("8*5=40");
        System.out.println("8*6=48");
        System.out.println("8*7=56");
        System.out.println("8*8=64");
        System.out.println("8*9=72");
        System.out.println();
        System.out.println("9*1=9");
        System.out.println("9*2=18");
        System.out.println("9*3=27");
        System.out.println("9*4=36");
        System.out.println("9*5=45");
        System.out.println("9*6=54");
        System.out.println("9*7=63");
        System.out.println("9*8=72");
        System.out.println("9*9=81");
        System.out.println();
    }
 
방법은 모르겠는데 일단 나열했다.
 
공통된게 보인다. 2단 3단 4단…..을 변수로 바꾸면 복붙이 쉬울 것 같다.
 
int x;
        x = 2;
        System.out.println(x + "*1=" + (x * 1));
        System.out.println(x + "*2=" + (x * 2));
        System.out.println(x + "*3=" + (x * 3));
        System.out.println(x + "*4=" + (x * 4));
        System.out.println(x + "*5=" + (x * 5));
        System.out.println(x + "*6=" + (x * 6));
        System.out.println(x + "*7=" + (x * 7));
        System.out.println(x + "*8=" + (x * 8));
        System.out.println(x + "*9=" + (x * 9));
        System.out.println();
 
x를 변수로 식을 만들었다. 이러면 x 값만 바꾸면 쉽게 복붙할 수 있다.
 
public static void main(String[] args) {
        int x;
        x = 2;
        System.out.println(x + "*1=" + (x * 1));
        System.out.println(x + "*2=" + (x * 2));
        System.out.println(x + "*3=" + (x * 3));
        System.out.println(x + "*4=" + (x * 4));
        System.out.println(x + "*5=" + (x * 5));
        System.out.println(x + "*6=" + (x * 6));
        System.out.println(x + "*7=" + (x * 7));
        System.out.println(x + "*8=" + (x * 8));
        System.out.println(x + "*9=" + (x * 9));
        System.out.println();
        x = 3;
        System.out.println(x + "*1=" + (x * 1));
        System.out.println(x + "*2=" + (x * 2));
        System.out.println(x + "*3=" + (x * 3));
        System.out.println(x + "*4=" + (x * 4));
        System.out.println(x + "*5=" + (x * 5));
        System.out.println(x + "*6=" + (x * 6));
        System.out.println(x + "*7=" + (x * 7));
        System.out.println(x + "*8=" + (x * 8));
        System.out.println(x + "*9=" + (x * 9));
        System.out.println();
        x = 4;
        System.out.println(x + "*1=" + (x * 1));
        System.out.println(x + "*2=" + (x * 2));
        System.out.println(x + "*3=" + (x * 3));
        System.out.println(x + "*4=" + (x * 4));
        System.out.println(x + "*5=" + (x * 5));
        System.out.println(x + "*6=" + (x * 6));
        System.out.println(x + "*7=" + (x * 7));
        System.out.println(x + "*8=" + (x * 8));
        System.out.println(x + "*9=" + (x * 9));
        System.out.println();
        x = 5;
        System.out.println(x + "*1=" + (x * 1));
        System.out.println(x + "*2=" + (x * 2));
        System.out.println(x + "*3=" + (x * 3));
        System.out.println(x + "*4=" + (x * 4));
        System.out.println(x + "*5=" + (x * 5));
        System.out.println(x + "*6=" + (x * 6));
        System.out.println(x + "*7=" + (x * 7));
        System.out.println(x + "*8=" + (x * 8));
        System.out.println(x + "*9=" + (x * 9));
        System.out.println();
        x = 6;
        System.out.println(x + "*1=" + (x * 1));
        System.out.println(x + "*2=" + (x * 2));
        System.out.println(x + "*3=" + (x * 3));
        System.out.println(x + "*4=" + (x * 4));
        System.out.println(x + "*5=" + (x * 5));
        System.out.println(x + "*6=" + (x * 6));
        System.out.println(x + "*7=" + (x * 7));
        System.out.println(x + "*8=" + (x * 8));
        System.out.println(x + "*9=" + (x * 9));
        System.out.println();
        x = 7;
        System.out.println(x + "*1=" + (x * 1));
        System.out.println(x + "*2=" + (x * 2));
        System.out.println(x + "*3=" + (x * 3));
        System.out.println(x + "*4=" + (x * 4));
        System.out.println(x + "*5=" + (x * 5));
        System.out.println(x + "*6=" + (x * 6));
        System.out.println(x + "*7=" + (x * 7));
        System.out.println(x + "*8=" + (x * 8));
        System.out.println(x + "*9=" + (x * 9));
        System.out.println();
        x = 8;
        System.out.println(x + "*1=" + (x * 1));
        System.out.println(x + "*2=" + (x * 2));
        System.out.println(x + "*3=" + (x * 3));
        System.out.println(x + "*4=" + (x * 4));
        System.out.println(x + "*5=" + (x * 5));
        System.out.println(x + "*6=" + (x * 6));
        System.out.println(x + "*7=" + (x * 7));
        System.out.println(x + "*8=" + (x * 8));
        System.out.println(x + "*9=" + (x * 9));
        System.out.println();
        x = 9;
        System.out.println(x + "*1=" + (x * 1));
        System.out.println(x + "*2=" + (x * 2));
        System.out.println(x + "*3=" + (x * 3));
        System.out.println(x + "*4=" + (x * 4));
        System.out.println(x + "*5=" + (x * 5));
        System.out.println(x + "*6=" + (x * 6));
        System.out.println(x + "*7=" + (x * 7));
        System.out.println(x + "*8=" + (x * 8));
        System.out.println(x + "*9=" + (x * 9));
        System.out.println();


    }
 
너무 길다. 반복문을 쓰자.
 
public static void main(String[] args) {

        for (int x = 2; x <= 9; x++) {
            System.out.println(x + "*1=" + (x * 1));
            System.out.println(x + "*2=" + (x * 2));
            System.out.println(x + "*3=" + (x * 3));
            System.out.println(x + "*4=" + (x * 4));
            System.out.println(x + "*5=" + (x * 5));
            System.out.println(x + "*6=" + (x * 6));
            System.out.println(x + "*7=" + (x * 7));
            System.out.println(x + "*8=" + (x * 8));
            System.out.println(x + "*9=" + (x * 9));
            System.out.println();
        }

    }
 
반복문을 활용해서 x 를 2~9까지 반복했다.
 
더 줄일 수 있을 것 같다.
 
public static void main(String[] args) {
        for (int x = 2; x <= 9; x++) {
            for (int i = 1; i <= 9; i++) {
                System.out.println(x + "*" + i + "=" + (x * i));
            }
            System.out.println();
        }
    }
반복문 두 번으로 구구단을 완성했다.
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