编程技巧与技术领域概览-优快云博客

【程序31】
题目：将一个数组逆序输出。

import java.util.*;
public class lianxi31 {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int a[] = new int[20];
		System.out.println("请输入多个正整数（输入-1表示结束）：");
		int i=0,j;
		do{
			a[i]=s.nextInt();
			i++;
		}while (a[i-1]!=-1);
		System.out.println("你输入的数组为：");
		for( j=0; j<i-1; j++) {
			System.out.print(a[j]+"   ");
		}
		System.out.println("\n数组逆序输出为：");
		for( j=i-2; j>=0; j=j-1) {
			System.out.print(a[j]+"   ");
		}
    <span style="white-space:pre">	</span>}
}

【程序32】
题目：取一个整数a从右端开始的4～7位。

import java.util.*;
public class lianxi32 {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		System.out.print("请输入一个7位以上的正整数：");
		long a = s.nextLong();
		String ss = Long.toString(a);
		char[] ch = ss.toCharArray();
		int j=ch.length;
		if (j<7){System.out.println("输入错误！");}
		else {
			System.out.println("截取从右端开始的4～7位是："+ch[j-7]+ch[j-6]+ch[j-5]+ch[j-4]);
		}
	} 
}

【程序33】
题目：打印出杨辉三角形（要求打印出10行如下图）
            1
          1    1
        1    2    1
      1    3    3    1
    1    4    6    4    1
1    5    10    10    5    1
…………

public class lianxi33 {
	public static void main(String[] args) {
		int[][] a = new int[10][10];
		for (int i = 0; i < 10; i++) {
			a[i][i] = 1;
			a[i][0] = 1;
		}
		for (int i = 2; i < 10; i++) {
			for (int j = 1; j < i; j++) {
				a[i][j] = a[i - 1][j - 1] + a[i - 1][j];
			}
		}
		for (int i = 0; i < 10; i++) {
			for (int k = 0; k < 2 * (10 - i) - 1; k++) {
				System.out.print(" ");
			}
			for (int j = 0; j <= i; j++) {
				System.out.print(a[i][j] + "   ");
			}
			System.out.println();
		}
	}
}

【程序34】
题目：输入3个数a,b,c，按大小顺序输出。

import java.util.Scanner;

public class lianxi34 {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		System.out.println("请输入3个整数：");
		int a = s.nextInt();
		int b = s.nextInt();
		int c = s.nextInt();
		if (a < b) {
			int t = a;
			a = b;
			b = t;
		}
		if (a < c) {
			int t = a;
			a = c;
			c = t;
		}
		if (b < c) {
			int t = b;
			b = c;
			c = t;
		}
		System.out.println("从大到小的顺序输出:");
		System.out.println(a + " " + b + " " + c);
	}
}

【程序35】
题目：输入数组，最大的与第一个元素交换，最小的与最后一个元素交换，输出数组。

import java.util.*;
public class lianxi35 {
	public static void main(String[] args) {
		int N = 8;
		int[] a = new int [N];
		Scanner s = new Scanner(System.in);
		int idx1 = 0, idx2 = 0;
		System.out.println("请输入8个整数：");
		for(int i=0; i<N; i++) {
			a[i] = s.nextInt();
		}
		System.out.println("你输入的数组为：");
		for(int i=0; i<N; i++) {
			System.out.print(a[i] + " ");
		}
		int max =a[0], min = a[0];
		for(int i=0; i<N; i++) {
			if(a[i] > max) {
				max = a[i];
				idx1 = i;
			} 
			if(a[i] < min) {
				min = a[i];
				idx2 = i;
			}
		} 
		if(idx1 != 0) {
			int temp = a[0];
			a[0] = a[idx1];
			a[idx1] = temp;
		}
		if(idx2 != N-1) {
			int temp = a[N-1];
			a[N-1] = a[idx2];
			a[idx2] = temp;
		}
		System.out.println("\n交换后的数组为：");
		for(int i=0; i<N; i++) {
			System.out.print(a[i] + " ");
		}
	}
}

【程序36】
题目：有n个整数，使其前面各数顺序向后移m个位置，最后m个数变成最前面的m个数

import java.util.Scanner;

public class lianxi36 {
	public static void main(String[] args) {
		int N = 10;
		int[] a = new int[N];
		Scanner s = new Scanner(System.in);
		System.out.println("请输入10个整数：");
		for (int i = 0; i < N; i++) {
			a[i] = s.nextInt();
		}
		System.out.print("你输入的数组为：");
		for (int i = 0; i < N; i++) {
			System.out.print(a[i] + " ");
		}
		System.out.print("\n请输入向后移动的位数：");
		int m = s.nextInt();
		int[] b = new int[m];
		for (int i = 0; i < m; i++) {
			b[i] = a[N - m + i];
		}
		for (int i = N - 1; i >= m; i--) {
			a[i] = a[i - m];
		}
		for (int i = 0; i < m; i++) {
			a[i] = b[i];
		}
		System.out.print("位移后的数组是：");
		for (int i = 0; i < N; i++) {
			System.out.print(a[i] + " ");
		}
	}
}

【程序37】
题目：有n个人围成一圈，顺序排号。从第一个人开始报数（从1到3报数），凡报到3的人退出圈子，问最后留下的是原来第几号的那位。

import java.util.Scanner;

public class lianxi37 {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		System.out.print("请输入排成一圈的人数：");
		int n = s.nextInt();
		boolean[] arr = new boolean[n];
		for (int i = 0; i < arr.length; i++) {
			arr[i] = true;
		}
		int leftCount = n;
		int countNum = 0;
		int index = 0;
		while (leftCount > 1) {
			if (arr[index] == true) {
				countNum++;
				if (countNum == 3) {
					countNum = 0;
					arr[index] = false;
					leftCount--;
				}
			}
			index++;
			if (index == n) {
				index = 0;
			}
		}
		for (int i = 0; i < n; i++) {
			if (arr[i] == true) {
				System.out.println("原排在第" + (i + 1) + "位的人留下了。");
			}
		}
	}
}

【程序38】
题目：写一个函数，求一个字符串的长度，在main函数中输入字符串，并输出其长度。
/*………………
*……题目意思似乎不能用length()函数     */
不用函数做不出
【程序39】
题目：编写一个函数，输入n为偶数时，调用函数求1/2+1/4+...+1/n,当输入n为奇数时，调用函数1/1+1/3+...+1/n(利用指针函数)
//没有利用指针函数

import java.util.*;

public class lianxi39 {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		System.out.print("请输入一个正整数 n= ");
		int n = s.nextInt();
		System.out.println("相应数列的和为：" + sum(n));
	}

	public static double sum(int n) {
		double res = 0;
		if (n % 2 == 0) {
			for (int i = 2; i <= n; i += 2) {
				res += (double) 1 / i;
			}
		} else {
			for (int i = 1; i <= n; i += 2) {
				res += (double) 1 / i;
			}
		}
		return res;
	}
}

【程序40】
题目：字符串排序。

public class lianxi40 {
	public static void main(String[] args) {
		int N = 5;
		String temp = null;
		String[] s = new String[N];
		s[0] = "matter";
		s[1] = "state";
		s[2] = "solid";
		s[3] = "liquid";
		s[4] = "gas";
		for (int i = 0; i < N; i++) {
			for (int j = i + 1; j < N; j++) {
				if (compare(s[i], s[j]) == false) {
					temp = s[i];
					s[i] = s[j];
					s[j] = temp;
				}
			}
		}
		for (int i = 0; i < N; i++) {
			System.out.println(s[i]);
		}
	}

	static boolean compare(String s1, String s2) {
		boolean result = true;
		for (int i = 0; i < s1.length() && i < s2.length(); i++) {
			if (s1.charAt(i) > s2.charAt(i)) {
				result = false;
				break;
			} else if (s1.charAt(i) < s2.charAt(i)) {
				result = true;
				break;
			} else {
				if (s1.length() < s2.length()) {
					result = true;
				} else {
					result = false;
				}
			}
		}
		return result;
	}
}