嵌套 For 循环广场 - Java

Question

我是 Java 新手，我正在使用嵌套 for 循环制作两个三角形的正方形。它应该看起来像这样：

+ + + + + 
* + + + + 
* * + + + 
* * * + + 
* * * * + 

到目前为止我的代码看起来像这样：

for (int i = 0; i < 5; i++) {             
for (int j = 0; j < i; j++) {               
System.out.print("* ");             
}  
System.out.println();

但它给我的只是广场的星形部分。我不知道如何离开这里。有人可以帮忙吗？

Answer 1

添加

i

星星后，请添加

5-i

加号

int lineLength = 5;
for (int i = 0; i < lineLength; i++) {
    for (int j = 0; j < i; j++) {
        System.out.print("* ");
    }
    for (int j = 0; j < lineLength - i; j++) {
        System.out.print("+ ");
    }
    System.out.println();
}

---

您可以使用

String.repeat

来简化代码

int lineLength = 5;
for (int i = 0; i < lineLength; i++) {
    System.out.println("* ".repeat(i) + "+ ".repeat(lineLength - i));
}

Answer 2

编辑添加解释。

第一步是创建一个 5 x 5 的网格。我们可以通过创建两个 for 循环（一个在另一个循环中）来做到这一点。内部 for 循环将打印一行

* 

，外部 for 循环将在每行后打印一个新行。

下一步是确定何时打印

+ 

而不是

* 

。对于您的情况，简单的大于 (

y > x

) 就可以了。

for (int y = 0; y < 5; y++) {
    for (int x = 0; x < 5; x++) {
        System.out.print(y > x ? "* " : "+ ");
    }
    System.out.println();
}

使用 Desmos 图形计算器进行演示。
请注意，y 轴是反向的，您可以使用

-y > x

来获得正确的方向

Answer 3

您可以利用 Arrays#fill 方法来预填充 char 的二维数组。

然后，迭代将相应的索引替换为星号。

char[][] characters = new char[5][5];
for (char[] row : characters) Arrays.fill(row, '+');
int count = 0;
for (char[] row : characters) {
    for (int index = 0; index < count; index++)
        row[index] = '*';
    count++;
}
int index = 0;
for (char[] row : characters) {
    for (char character : row) {
        if (index++ != 0) System.out.print(" ");
        System.out.print(character);
    }
    index = 0;
    System.out.println();
}

输出

+ + + + + 
* + + + + 
* * + + + 
* * * + + 
* * * * + 

此外，您可以使用允许输入值的方法。

void draw(int size, char charA, char charB) {
    char[][] characters = new char[size][size];
    for (char[] row : characters) Arrays.fill(row, charB);
    int count = 0;
    for (char[] row : characters) {
        for (int index = 0; index < count; index++)
            row[index] = charA;
        count++;
    }
    int index = 0;
    for (char[] row : characters) {
        for (char character : row) {
            if (index++ != 0) System.out.print(" ");
            System.out.print(character);
        }
        index = 0;
        System.out.println();
    }
}

示例用法和输出。

draw(20, '@', '-');

- - - - - - - - - - - - - - - - - - - -
@ - - - - - - - - - - - - - - - - - - -
@ @ - - - - - - - - - - - - - - - - - -
@ @ @ - - - - - - - - - - - - - - - - -
@ @ @ @ - - - - - - - - - - - - - - - -
@ @ @ @ @ - - - - - - - - - - - - - - -
@ @ @ @ @ @ - - - - - - - - - - - - - -
@ @ @ @ @ @ @ - - - - - - - - - - - - -
@ @ @ @ @ @ @ @ - - - - - - - - - - - -
@ @ @ @ @ @ @ @ @ - - - - - - - - - - -
@ @ @ @ @ @ @ @ @ @ - - - - - - - - - -
@ @ @ @ @ @ @ @ @ @ @ - - - - - - - - -
@ @ @ @ @ @ @ @ @ @ @ @ - - - - - - - -
@ @ @ @ @ @ @ @ @ @ @ @ @ - - - - - - -
@ @ @ @ @ @ @ @ @ @ @ @ @ @ - - - - - -
@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ - - - - -
@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ - - - -
@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ - - -
@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ - -
@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ -