『一步一脚印』Java算法比赛基本输入输出

1. 类名定义

public class Main

2. 多数据读入

Scanner in = new Scanner(System.in);
while(in.hasNext()) 

3. 读入整数

int n = sc.nextInt(); //相当于scanf("%d", &n); 

4. 读入一个字符串

String s = sc.next(); //scanf("%s", s);

5. 读一个浮点数

double t = sc.nextDouble(); //scanf("%lf", &t); 

6. 读一整行

String s = sc.nextLine(); //gets(s);

7.数字排序（先小后大）

//数字排序
int[] num = {8,3,2,4,5};
Arrays.sort(num);for(int i = 0;i<num.length;i++)
{System.out.print(num[i]);
}
System.out.println();

8.字符串排序（先大后小）

//字符串排序
String[] s={"t","z","A","b"};
Arrays.sort(s);for(int i = 0;i<s.length;i++)
{System.out.print(s[i]);
}
System.out.println();

9.严格按照字母表排序

String[] s={"t","z","A","b"};
Arrays.sort(s,String.CASE_INSENSITIVE_ORDER);
for(int i = 0;i<s.length;i++)
{System.out.print(s[i]);
}
System.out.println();

10.忽略大小写反向排序

//字符串排序
String[] s={"t","z","A","b"};
Arrays.sort(s,String.CASE_INSENSITIVE_ORDER);
Collections.reverse(Arrays.asList(s));for(int i = 0;i<s.length;i++)
{System.out.print(s[i]);
}
System.out.println();

11.对象的排序

Car car1 = new Car(45);
Car car2 = new Car(6);
Car car3 = new Car(2);
Car car4 = new Car(4);
Car car5 = new Car(475);
Car[] cars = {car1,car2,car3,car4,car5};
Arrays.sort(cars,new CarComparator());
for(int i = 0 ;i < cars.length;i++)
{System.out.println(cars[i]);
}
System.out.println();class Car
{private int number;public Car(int number) {this.number = number;}public int getNumber() {return number;}public void setNumber(int number) {this.number = number;}@Overridepublic String toString() {return "Car{" +"number=" + number +'}';}
}class CarComparator implements Comparator
{@Overridepublic int compare(Object o1, Object o2) {Car car1 = (Car) o1;Car car2 = (Car) o2;if(car1.getNumber() < car2.getNumber())return -1;else  if (car1.getNumber() > car2.getNumber())return 1;return 0;}
}

12.Vector基本使用

Vector v = new Vector(4);
v.add("test");
v.add("tes2");
v.add("test3454");
for(int i = 0;i < v.size();i++)
{System.out.print(v.get(i));
}
System.out.println();

13.栈使用

Stack st = new Stack();
st.push("1");
st.push("2");
st.push("3");
for(Iterator it = st.iterator();it.hasNext();)
{String tmp =(String) it.next();System.out.println(tmp);
}

14.队列的使用

//队列使用
Queue<Integer> q = new LinkedList<Integer>();
q.offer(1);
q.offer(2);
q.offer(3);
//返回第一个元素并删除
System.out.println(q.poll());
//返回第一个元素
System.out.println(q.peek());
System.out.println(q.element());

15.填充数组

int[] a = new int[10];
Arrays.fill(a, -1);
System.out.println(Arrays.toString(a));

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