嵌套循环中的输出

Question

我正在尝试获取此输出：

123454321
1234 4321
123   321
12     21
1       1

我试过先这样做：

12345
1234
123
12
1

然后，放一个'\t'然后把它放在上面的旁边：

4321
4321
321
21
1 

Answer 1

下面的代码给出了你提到的输出

package com.hello;

public class Test {

/**
 * @param args
 */
public static void main(String[] args) {
    printNumbers(5,5);
}

private static void printNumbers(int max,int iteration)
{
    String line ="";
    int NoOfSpaces = (max-iteration)*2 -1;

    if(iteration == 0)
        return;
    for(int i=1;i<=iteration;i++)
        line = line+i;
    for(int i =0;i<NoOfSpaces;i++)
        line = line+" ";
    if(max != iteration)
        line = line +iteration;
    for(int i=iteration-1;i>=1;i--)
        line = line +i;
    System.out.println(line);
    printNumbers(max,--iteration);

  }
}

如果您还有其他问题，请告诉我....

Answer 2

问题可以使用以下代码递归求解：

public static void recurseForward(int to, int space) {
    if (to == 0) {
        return;
    }
    for (int i = 1; i <= to; i++) {
        System.out.print(i);
    }
    for (int i = 0; i < space; i++) {
        System.out.print(" ");
    }
    recurseBackward(to, space);
}

public static void recurseBackward(int from, int space) {
    for (int i = 0; i < space; i++) {
        System.out.print(" ");
    }
    for (int i = from; i > 0; i--) {
        System.out.print(i);
    }
    System.out.println("");
    recurseForward(from - 1, space + 1);
}

public static void main(String[] args) {
    recurseForward(5, 0);
}