JAVA经典题目汇总

public class Fibonacci {
public static void main(String[] args) {
int[] fib = new int[20];
fib[0] = 0;
fib[1] = 1;
for(int i = 2; i < fib.length; i++)
fib[i] = fib[i-1] + fib[i-2];
for(int i = 0; i < fib.length; i++)
System.out.print(fib[i] + " ");
System.out.println();
}
}

import java.awt.*;
import javax.swing.*;
public class Pascal extends JFrame {
public Pascal() {
setBackground(Color.white);
setTitle("巴斯卡三角形");
setSize(520, 350);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
show();
}
private long combi(int n, int r){
int i;
long p = 1;
for(i = 1; i <= r; i++)
p = p * (n-i+1) / i;

return p;
}
public void paint(Graphics g) {
final int N = 12;
int n, r, t;
for(n = 0; n <= N; n++) {
for(r = 0; r <= n; r++)
g.drawString(" " + combi(n, r),
(N-n)*20 + r * 40, n * 20 + 50);
}
}
public static void main(String args[]) {
Pascal frm = new Pascal();
}
}

import java.io.*;
public class ThreeColorsFlags {
private void swap(char[] flags, int x, int y) {
char temp;
temp = flags[x];
flags[x] = flags[y];
flags[y] = temp;
}

public String move(char[] flags) {
int wFlag = 0;
int bFlag = 0;
int rFlag = flags.length - 1;

while(wFlag <= rFlag) {
if(flags[wFlag] == 'W') {
wFlag++;
}
else if(flags[wFlag] == 'B') {
swap(flags, bFlag, wFlag);
bFlag++;
wFlag++;
}
else {
while(wFlag < rFlag && flags[rFlag] == 'R')
rFlag--;
swap(flags, rFlag, wFlag);
rFlag--;
}
}

return new String(flags);
}

public static void main(String[] args)
throws IOException {
BufferedReader buf;
buf = new BufferedReader(
new InputStreamReader(System.in));
System.out.print("输入三色旗顺序（ex. RWBBWRWR）：");
String flags = buf.readLine();

ThreeColorsFlags threeColorsFlag = new ThreeColorsFlags();
flags = threeColorsFlag.move(
flags.toUpperCase().toCharArray());

System.out.println("移动顺序后：" + flags);
}
}

public class Mouse {
private int startI, startJ;  // 入口
private int endI, endJ;  // 出口
private boolean success = false;

public static void main(String[] args) {
int[][] maze = {{2, 2, 2, 2, 2, 2, 2},
{2, 0, 0, 0, 0, 0, 2},
{2, 0, 2, 0, 2, 0, 2},
{2, 0, 0, 2, 0, 2, 2},
{2, 2, 0, 2, 0, 2, 2},
{2, 0, 0, 0, 0, 0, 2},
{2, 2, 2, 2, 2, 2, 2}};

System.out.println("显示迷宫：");
for(int i = 0; i < maze.length; i++) {
for(int j = 0; j < maze[0].length; j++)
if(maze[j] == 2)
System.out.print("█");
else
System.out.print("  ");
System.out.println();
}
Mouse mouse = new Mouse();
mouse.setStart(1, 1);
mouse.setEnd(5, 5);

if(!mouse.go(maze)) {
System.out.println("/n没有找到出口！");
}
else {
System.out.println("/n找到出口！");
for(int i = 0; i < maze.length; i++) {
for(int j = 0; j < maze[0].length; j++) {
if(maze[j] == 2)
System.out.print("█");
else if(maze[j] == 1)
System.out.print("◇");
else
System.out.print("  ");
}
System.out.println();
}
}
}

public void setStart(int i, int j) {
this.startI = i;
this.startJ = j;
}

public void setEnd(int i, int j) {
this.endI = i;
this.endJ = j;
}

public boolean go(int[][] maze) {
return visit(maze, startI, startJ);
}

private boolean visit(int[][] maze, int i, int j) {
maze[j] = 1;
if(i == endI && j == endJ)
success = true;
if(!success && maze[j+1] == 0)
visit(maze, i, j+1);
if(!success && maze[i+1][j] == 0)
visit(maze, i+1, j);
if(!success && maze[j-1] == 0)
visit(maze, i, j-1);
if(!success && maze[i-1][j] == 0)
visit(maze, i-1, j);
if(!success)
maze[j] = 0;

return success;
}
}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class LifeGame {
private boolean[][] map;
private boolean[][] newmap;

public LifeGame(int maxRow, int maxColumn) {
map = new boolean[maxRow][maxColumn];
newmap = new boolean[maxRow][maxColumn];
}

public void setCell(int x, int y) {
map[x][y] = true;
}

public void next() {
for(int row = 0; row < map.length; row++) {
for(int col = 0; col < map[0].length; col++) {
switch (neighbors(row, col)) {
case 0:
case 1:
case 4:
case 5:
case 6:
case 7:
case 8:
newmap[row][col] = false;
break;
case 2:
newmap[row][col] = map[row][col];
break;
case 3:
newmap[row][col] = true;
break;
}
}
}
copyMap();
}
public void outputMap() throws IOException {
System.out.println("/n/nGame of life cell status");
for(int row = 0; row < map.length; row++) {
System.out.print("/n ");
for(int col = 0; col < map[0].length; col++)
if(map[row][col] == true)
System.out.print('#');
else
System.out.print('-');
}
}

private void copyMap() {
for(int row = 0; row < map.length; row++)
for(int col = 0; col < map[0].length; col++)
map[row][col] = newmap[row][col];
}

private int neighbors(int row, int col) {
int count = 0;
for(int r = row-1; r <= row+1; r++)
for(int c = col-1; c <= col+1; c++) {
if(r < 0 || r >= map.length ||
c < 0 || c >= map[0].length)
continue;
if(map[r][c] == true)
count++;
}
if(map[row][col] == true)
count--;

return count;
}

public static void main(String[] args)
throws NumberFormatException, IOException {
BufferedReader bufReader =
new BufferedReader(
new InputStreamReader(System.in));

LifeGame game = new LifeGame(10, 25);

System.out.println("Game of life Program");
System.out.println(
"Enter x, y where x, y is living cell");
System.out.println("0 <= x < 10, 0 <= y < 25");
System.out.println("Terminate with x, y = -1, -1");

while(true) {
String[] strs = bufReader.readLine().split(" ");
int row = Integer.parseInt(strs[0]);
int col = Integer.parseInt(strs[1]);
if(0 <= row && row < 10 && 0 <= col && row < 25)
game.setCell(row, col);
else if(row == -1 || col == -1) {
break;
}
else {
System.out.print(
"(x, y) exceeds map ranage!");
}
}

while(true) {
game.outputMap();
game.next();
System.out.print(
"/nContinue next Generation ? ");

String ans = bufReader.readLine().toUpperCase();
if(!ans.equals("Y"))
break;
}
}
}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class StringMatch {
private int[] skip;
private int p;
private String str;
private String key;

public StringMatch(String key) {
skip = new int[256];
this.key = key;

for(int k = 0; k <= 255; k++)
skip[k] = key.length();
for(int k = 0; k < key.length() - 1; k++)
skip[key.charAt(k)] = key.length() - k - 1;
}

public void search(String str) {
this.str = str;
p = search(key.length()-1, str, key);
}

private int search(int p, String input, String key) {
while(p < input.length()) {
String tmp = input.substring(
p-key.length()+1, p+1);
if(tmp.equals(key))  // 比较两个字符串是否相同
return p-key.length()+1;
p += skip[input.charAt(p)];
}
return -1;
}

public boolean hasNext() {
return (p != -1);
}

public String next() {
String tmp = str.substring(p);
p = search(p+key.length()+1, str, key);
return tmp;
}

public static void main(String[] args)
throws IOException {
BufferedReader bufReader =
new BufferedReader(
new InputStreamReader(System.in));

System.out.print("请输入字符串：");
String str = bufReader.readLine();
System.out.print("请输入搜寻关键字：");
String key = bufReader.readLine();

StringMatch strMatch = new StringMatch(key);
strMatch.search(str);
while(strMatch.hasNext()) {
System.out.println(strMatch.next());
}
}
}

class Fruit {
private String name;
private int size;
private int price;

public Fruit(String name, int size, int price) {
this.name = name;
this.size = size;
this.price = price;
}

public String getName() {
return name;
}
public int getPrice() {
return price;
}
public int getSize() {
return size;
}
}
public class Knapsack {
public static void main(String[] args) {
final int MAX = 8;
final int MIN = 1;
int[] item = new int[MAX+1];
int[] value = new int[MAX+1];
Fruit fruits[] = {
new Fruit("李子", 4, 4500),
new Fruit("苹果", 5, 5700),
new Fruit("桔子", 2, 2250),
new Fruit("草莓", 1, 1100),
new Fruit("甜瓜", 6, 6700)};
for(int i = 0; i < fruits.length; i++) {
for(int s = fruits[i].getSize(); s <= MAX; s++) {
int p = s - fruits[i].getSize();
int newvalue = value[p] +
fruits[i].getPrice();
if(newvalue > value[s]) {// 找到阶段最佳解
value[s] = newvalue;
item[s] = i;
}
}
}
System.out.println("物品/t价格");
for(int i = MAX;
i >= MIN;
i = i - fruits[item[i]].getSize()) {
System.out.println(fruits[item[i]].getName()+
"/t" + fruits[item[i]].getPrice());
}
System.out.println("合计/t" + value[MAX]);
}
}

import java.io.*;
public class Hanoi {
public static void main(String args[]) throws IOException {
int n;
BufferedReader buf;
buf = new BufferedReader(new InputStreamReader(System.in));
System.out.print("请输入盘子个数");
n = Integer.parseInt(buf.readLine());
Hanoi hanoi = new Hanoi();
hanoi.move(n, 'A', 'B', 'C');
}
public void move(int n, char a, char b, char c) {
if(n == 1)
System.out.println("盘 " + n + " 由 " + a + " 移至 " + c);
else {
move(n - 1, a, c, b);
System.out.println("盘 " + n + " 由 " + a + " 移至 " + c);
move(n - 1, b, a, c);
}
}
}