1.结构体排序
import java.util.*; public class Main { static class Node{ //内部静态类 String s; int x; } static class compareTo implements Comparator<Node>{ //升序排序 public int compare(Node a,Node b){ if(a.x>b.x) return 1; else if(a.x==b.x) return 0; else return -1; } } // static class compareTo implements Comparator<Object>{ // public int compare(Object a, Object b){ // Node t1 = (Node) a; // Node t2 = (Node) b; // if(t1.x > t2.x) return 1; // else if(t1.x == t2.x) return 0; // else return -1; // } // } static Scanner sc = new Scanner(System.in); static Node[] s = new Node[105]; public static void main(String[] args){ int n = sc.nextInt(); for(int i = 1; i <= n; i++){ s[i] = new Node(); s[i].s = sc.next(); s[i].x = sc.nextInt(); } Arrays.sort(s, 1, n+1, new compareTo()); for(int i = 1; i <= n; i++){ if(i > 1) System.out.print(" "); System.out.print(s[i].s + " " + s[i].x); } System.out.println(); } }
2.循环式并查集
static int[] f = new int[100005]; static int find(int x) { //循环式路径压缩 int p=x; while(f[p]!=p){ p=f[p]; } while(x!=p){ int t=f[x]; f[x]=p; x=t; } return x; }
3.矩阵快速幂
import java.util.Scanner; public class Main { static final long MOD = 1010101010; static Scanner sc = new Scanner(System.in); static class mat{ long[][] a = new long[10][10]; } static mat mul(mat x,mat y) { mat a = new mat(); for(int i=1;i<=2;i++) { for(int j=1;j<=2;j++) { for(int k=1;k<=2;k++) { a.a[i][j]+=x.a[i][k]*y.a[k][j]%MOD; a.a[i][j]%=MOD; } } } return a; } static long qMod(mat a,long n) { mat t = new mat(); t.a[1][1]=1;t.a[1][2]=1; t.a[2][1]=1;t.a[2][2]=0; while(n>0) { if(n%2==1) a=mul(t,a); n>>=1; t=mul(t,t); } return a.a[1][1]; } public static void main(String[] args) { long n=sc.nextLong(); if(n==1) { System.out.println(1); } else if(n==2) { System.out.println(2); } else { mat a = new mat(); a.a[1][1]=2; a.a[2][1]=1; System.out.println(qMod(a,n-2)); } } }
4.结构体队列陷阱
import java.util.ArrayDeque; public class Main { static class Node{ int x,y; public Node(int x,int y) { //每次新建一个对象存值 this.x=x; this.y=y; } } static ArrayDeque<Node> q = new ArrayDeque<Node>(); public static void main(String[] args) { // Node no = new Node(); // no.x=1;no.y=1; // q.offerLast(no); // no = new Node(); //没有这句会对第一个值进行修改 // no.x=2;no.y=2; // q.offerLast(no); q.offerLast(new Node(1,1)); //规范写法 q.offerLast(new Node(2,2)); while(q.size()>0) { System.out.println(q.peekFirst().x); System.out.println(q.peekFirst().y); q.pollFirst(); } } }
5.优先队列
import java.util.Comparator; import java.util.PriorityQueue; class VowelComparator implements Comparator<String> { @Override public int compare(String x, String y) { if (getVowelCount(x) < getVowelCount(y)) { return -1; } else if (getVowelCount(x) > getVowelCount(y)) { return 1; } return 0; } public int getVowelCount(String word) { int vowel = 0; for (int i = 0; i < word.length(); i++) { char chr = word.charAt(i); if (chr == 'a' || chr == 'A' || chr == 'e' || chr == 'E' || chr == 'i' || chr == 'I' || chr == 'o' || chr == 'O' || chr == 'u' || chr == 'U') vowel++; } return vowel; } } public class Main { public static void main(String[] args) { Comparator<String> queueComparator = new VowelComparator(); PriorityQueue<String> priorityQueue = new PriorityQueue<String>(10, queueComparator); priorityQueue.add("orange"); priorityQueue.add("fig"); priorityQueue.add("watermelon"); priorityQueue.add("lemon"); while (priorityQueue.size() != 0) { System.out.println(priorityQueue.remove()); } } }
6.进制转换
进制转换7.输入挂
输入挂8.map映射
import java.util.*; public class Main { static Scanner sc = new Scanner(System.in); static int[] a = new int[105]; public static void main(String[] args){ int n,i; String key, maxk; int value, maxv; while(sc.hasNext()){ n=sc.nextInt(); if(n == 0) break; Map map = new HashMap(); Set set = map.keySet(); for(i = 1; i <= n; i++){ key = sc.next(); if(map.get(key)==null) value = 1; else{ value = (int) map.get(key); value++; } map.put(key, value); } Iterator iter = set.iterator(); maxv = 0;maxk = null; while(iter.hasNext()){ key = (String) iter.next(); value = (int) map.get(key); if(value > maxv){ maxk = key; maxv =value; } } System.out.println(maxk); } } }
9.宏定义
static final int MAX = 1005;
10.Set的使用
public class Demo4 { public static void main(String[] args) { //Set 集合存和取的顺序不一致。 Set hs = new HashSet(); hs.add("世界军事"); hs.add("兵器知识"); hs.add("舰船知识"); hs.add("汉和防务"); System.out.println(hs); // [舰船知识, 世界军事, 兵器知识, 汉和防务] Iterator it = hs.iterator(); while (it.hasNext()) { System.out.println(it.next()); } } }
11.程序计时
long startTime=System.currentTimeMillis();//记录开始时间 method();//此处为你调用的方法 long endTime=System.currentTimeMillis();//记录结束时间 double excTime=(double)(endTime-startTime)/1000; System.out.println("执行时间："+excTime+"s");
以下博客对java在ACM中的总结非常好，link一下。
ttp://www.cppblog.com/vontroy/archive/2010/05/24/116233.html
www.xuebuyuan.com/zh-hant/977823.html