java acm模式输入输出
之前刷leetcode都是核心代码模式，最近在准备面试发现不光要给出实现功能的函数，也要自己构造测试用例输入输出，稍微总结一下用法
输入格式
两种输入格式，在读入数据量大的情况下，格式1的速度会快些
import java.io.BufferedReader;
import java.io.InputStreamReader;
Scanner sc = new Scanner (new BufferedInputStream(System.in));
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import java.util.Scanner;
Scanner sc = new Scanner (System.in);
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下面开始读取
int n = sc.nextInt();
String s = sc.next();
double t = sc.nextDouble();
String s = sc.nextLine();
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判断是否有下一个输入
sc.hasNext()
sc.hasNextInt()
sc.hasNextDouble()
sc.hasNextLine()
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最后记得关闭输出流
输出格式
System.out.print();
System.out.println();
System.out.format();
System.out.printf();
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读入多个整数
Input 输入数据有多组，每组占一行，由一个整数组成
Sample Input
56
67
100
123
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc =new Scanner(System.in);
while(sc.hasNext()){
int score = sc.nextInt();
}
}
}
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输入多组整数
输入数据有多组，每组占2行，第一行为一个整数N，指示第二行包含N个实数
Sample Input
4
56.9 67.7 90.5 12.8
5
56.9 67.7 90.5 12.8
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc =new Scanner(System.in);
while(sc.hasNext()){
int n = sc.nextInt();
for(int i=0;i<n;i++){
double a = sc.nextDouble();
。。。。。。
}
}
}
}
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输入字符串
输入数据有多行，第一行是一个整数n，表示测试实例的个数，后面跟着n行，每行包括一个由字母和数字组成的字符串。
Sample Input
2
asdfasdf1
asdf1111111
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
for(int i=0;i<n;i++){
String str = sc.next();
......
}
}
}
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = Integer.parseInt(sc.nextLine());
for(int i=0;i<n;i++){
String str = sc.nextLine();
......
}
}
}
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输入链表
链表的数据结构
class ListNode {
int val;
ListNode next;
public ListNode(int val) {
this.val = val;
}
}
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将要调用的初始链表函数如下
public static ListNode InitListNode(int[] ints) {
ListNode head = new ListNode(0);
ListNode p = head;
for (int i = 0; i < ints.length; i++) {
p.next = new ListNode(ints[i]);
p = p.next;
}
return head.next;
}
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输入以逗号分隔的一串数字，比如1,2,3,4,5
Scanner scanner = new Scanner(System.in);
String str = scanner.next().toString();
String[] arr = str.split(",");
int[] ints = new int[arr.length];
for (int j = 0; j < ints.length; j++) {
ints[j] = Integer.parseInt(arr[j]);
}
ListNode head = InitListNode(ints);
scanner.close();
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输出，也是以字符串隔开的数字
while (myhead != null) {
if (myhead.next == null) {
System.out.print(myhead.val);
} else {
System.out.print(myhead.val + ",");
}
myhead = myhead.next;
}
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下面用反转链表举个例子，怎么将leetode中我们写好的核心代码融入输入输出中
注意如果main里面要调用该类的方法和类，要用static修饰，否则会报错
import java.util.Scanner;
class ListNode {
int val;
ListNode next;
public ListNode(int val) {
this.val = val;
}
}
public class ReverseList {
public static ListNode reverseList(ListNode head) {
ListNode prev = null;
ListNode curr = head;
while (curr != null) {
ListNode next = curr.next;
curr.next = prev;
prev = curr;
curr = next;
}
return prev;
}
public static ListNode InitListNode(int[] ints) {
ListNode head = new ListNode(0);
ListNode p = head;
for (int i = 0; i < ints.length; i++) {
p.next = new ListNode(ints[i]);
p = p.next;
}
return head.next;
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String str = scanner.next().toString();
String[] arr = str.split(",");
int[] ints = new int[arr.length];
for (int j = 0; j < ints.length; j++) {
ints[j] = Integer.parseInt(arr[j]);
}
ListNode head = InitListNode(ints);
scanner.close();
ListNode myhead = reverseList(head);
while (myhead != null) {
if (myhead.next == null) {
System.out.print(myhead.val);
} else {
System.out.print(myhead.val + ",");
}
myhead = myhead.next;
}
}
}
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输入二叉树
二叉树的数据结构
class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) { val = x; }
}
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