0421for循环各类题目

for循环要点

1.确认外层控制内容

2.确认内层控制内容

3.将打印内容与行号产生关系式

4.有的语句可以用if语句，根据字符的个数来增减char，优化代码

//部分类型只能输出奇数行，可在下半部分开始前，对行数做一个判断，根据讲述奇偶性调整自变量的取值；如下语句中的k
	int k = i;
	if (0 == line % 2) {
		k = i - 1;
	}

	for (int j = 1; j <= k; j++) {

//偶数行的一半就是行数/2，奇数行的中间一行可以放在上半部分，先定义下半部分行数为  int = line / 2 ;再用总行数减去下半部分得到上半部分数值
	int cn = 2 * i - 1;//cn == charNumber
	int bacCharNum = cn / 2;
	int froCharNum = cn - bacCharNum;

难度系数：重辣

/*

难度系数：重辣
     A
    ABA
   ABCBA
  ABCDCBA
 ABCDEDCBA
ABCDEFEDCBA
*/

class Demo8 {
	public static void main(String[] args) {

		char ch = 'A';
		int line = 10;

		for (int i = 1; i <= line;i++) {

			ch = 'A';

			//输出空格
			for (int j = 1; j <= line - i; j++) {
				System.out.print(" ");
			}

			int cn = 2 * i - 1;
			int bacCharNum = cn / 2;
			int froCharNum = cn - bacCharNum;

			//输出每行的前半部分
			for (int j = 1;j <= froCharNum ;j++) {
				System.out.print(ch);
				ch++;
			}

			//输出每行的后半部分
			ch -= 2;
			for (int j = 1;j <= bacCharNum ;j++) {
				System.out.print(ch);
				ch--;
			}
			System.out.println();
		}
	}
}
/*
输出结果：

         A
        ABA
       ABCBA
      ABCDCBA
     ABCDEDCBA
    ABCDEFEDCBA
   ABCDEFGFEDCBA
  ABCDEFGHGFEDCBA
 ABCDEFGHIHGFEDCBA
ABCDEFGHIJIHGFEDCBA
*/

//难度系数：重辣
//优化方案：将每行打印中的字母用if语句改写
/*
     A
    ABA
   ABCBA
  ABCDCBA
 ABCDEDCBA
ABCDEFEDCBA
*/

class Demo88 {
	public static void main(String[] args) {

		char ch = 'A';
		int line = 10;

		for (int i = 1; i <= line;i++) {

			ch = 'A';
			ch --;
			//输出空格
			for (int j = 1; j <= line - i; j++) {
				System.out.print(" ");
			}

			int cn = 2 * i - 1;
			int bacCharNum = cn / 2;
			int froCharNum = cn - bacCharNum;

			for (int j = 1;j <= cn ;j++) {
				if (j < froCharNum) {
					ch++;
				} else if (j == froCharNum) {
					ch++;
				} else {
					ch--;
				}
				System.out.print(ch);
			}
			System.out.println();
		}
	}
}

难度系数：魔鬼辣

/*
     A
    ABA
   ABCBA
  ABCDCBA
 ABCDEDCBA
ABCDEFEDCBA
 ABCDEDCBA
  ABCDCBA
   ABCBA
    ABA
     A
*/
class Demo9 {
	public static void main(String[] args) {

		char ch = 'A';
		int line = 11;//仅限奇数

		int downPart = line / 2;
		int upPart = line - downPart;

		for (int i = 1; i <= upPart;i++) {
			ch = 'A';
			for (int j = 1; j <= upPart - i; j++) {
				System.out.print(" ");
			}

			int cn = 2 * i - 1;
			int bacCharNum = cn / 2;
			int froCharNum = cn - bacCharNum;

			for (int j = 1;j <= froCharNum ;j++) {
				System.out.print(ch);
				ch++;
			}
				ch -= 2;
			for (int j = 1;j <= bacCharNum ;j++) {
				System.out.print(ch);
				ch--;
			}
			System.out.println();
		}

		for (int i = 1;i <= downPart; i++) {
			ch = 'A';

			int cn = 2 * downPart + 1 - 2 * i;
			int bacCharNum = cn / 2;
			int froCharNum = cn - bacCharNum;

			for (int j = 1; j <= i; j++) {
				System.out.print(" ");
			}

			for (int j = 1;j <= froCharNum; j++) {

				System.out.print(ch);
				ch ++;
			}
			ch -= 2;
			for (int j = 1;j <= bacCharNum; j++) {
				System.out.print(ch);
				ch --;
			}
			System.out.println();

		}
	}
}

/*
//难度系数：魔鬼辣
//优化方案：调整为偶数也可以

     A
    ABA
   ABCBA
  ABCDCBA
 ABCDEDCBA
ABCDEFEDCBA
ABCDEFEDCBA
 ABCDEDCBA
  ABCDCBA
   ABCBA
    ABA
     A
*/

class Demo99 {
	public static void main(String[] args) {

		char ch = 'A';
		int line = 12;

		int downPart = line / 2;
		int upPart = line - downPart;

		for (int i = 1; i <= upPart;i++) {
			ch = 'A';
			for (int j = 1; j <= upPart - i; j++) {
				System.out.print(" ");
			}

			int cn = 2 * i - 1;
			int bacCharNum = cn / 2;
			int froCharNum = cn - bacCharNum;

			for (int j = 1;j <= froCharNum ;j++) {
				System.out.print(ch);
				ch++;
			}
				ch -= 2;
			for (int j = 1;j <= bacCharNum ;j++) {
				System.out.print(ch);
				ch--;
			}
			System.out.println();
		}

		for (int i = 1;i <= downPart; i++) {
			ch = 'A';

			int cn = 2 * downPart + 1 - 2 * i;
			int bacCharNum = cn / 2;
			int froCharNum = cn - bacCharNum;

			int k = i;
			if (0 == line % 2) {
				k = i - 1;
			}

			for (int j = 1; j <= k; j++) {
				System.out.print(" ");
			}

			for (int j = 1;j <= froCharNum; j++) {

				System.out.print(ch);
				ch ++;
			}
			ch -= 2;
			for (int j = 1;j <= bacCharNum; j++) {
				System.out.print(ch);
				ch --;
			}			

			System.out.println();
		}
	}
}