入门经典编程题-菱形

题目

打印出n行的菱形（n为奇数）
例如：输入5 打印出如下图案（菱形）：

         * 
          *** 
       ***** 
          *** 
         *

分析

单层循环
此实现方法需要去寻找图形之间的数学规律

双层循环
将图形分割成上下两部分 分别打印
第一层循环按行打印
第二层循环：循环打印空格，循环打印*号

Java实现

单层循环的实现

首先理解此图形的代码实现

         * 
          *** 
       ***** 

public static void example05(){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int k = 0;
        int mid = n/2;
        for (int i = 0; i < n*(n+1)/2; i++) {
            if (i % n == 0 && i != 0) {
                k++;
                mid += n;
                System.out.println();
            }
            if ( mid-k <= i && i <= mid+k) {
                System.out.print("*");
            }else{
                System.out.print(" ");
            }
        }
    }

完整图形代码实现

public static void example05(){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int k = 0;
        int mid = n/2;
        for (int i = 0; i < n*(n+1)-1; i++) {
            if (i % n == 0 && i != 0) {
                mid += n;
                if (i < n*(n+1)/2) k++;
                else k--;
                System.out.println();
            }
            if ( mid-k <= i && i <= mid+k) {
                System.out.print("*");
            }else{
                System.out.print(" ");
            }
        }
    }

双循环打印

public static void example05_2(){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int k = 0;
        int mid = n/2;
        for (int i = 0; i < mid+1; i++) {
            for (int j = 0; j < mid-k; j++) {
                System.out.print(" ");
            }
            for (int j = mid-k ; j <= mid+k; j++) {
                System.out.print("*");
            }
            System.out.println();
            k++;
        }
        k = k-2;
        for (int i = 0; i < mid ; i++) {
            for (int j = 0; j < mid-k; j++) {
                System.out.print(" ");
            }
            for (int j = mid-k ; j <= mid+k; j++) {
                System.out.print("*");
            }
            System.out.println();
            k--;
        }
    }