JAVA.Arrays.sort(排序)
阿新 • • 發佈:2021-11-13
Arrays.sort
從小到大排序
常用方法:
Arrays.sort(陣列名,起始下表,終止下表)
Arrays.sort(陣列名)
舉例:
點選檢視程式碼
/** *輸入案例: *5 4 3 2 1 *輸出: *4.0 5.0 3.0 2.0 1.0 *1.0 2.0 3.0 4.0 5.0 **/ import java.util.*; import java.util.Arrays; public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); double[] a=new double[5]; for(int i=0;i<5;i++) { a[i]=sc.nextDouble(); } Arrays.sort(a,0,2); for (double t:a) { System.out.print(t+ " "); } System.out.println(); Arrays.sort(a); for (double t:a) { System.out.print(t+ " "); } System.out.println(); sc.close(); } }
從大到小
常用方法:
Arrays.sort(陣列名,起始下標,終止下標,new cmp() );
cmp函式:
public int compare(Object o1,Object o2)
{
//降序
if(o1<o2) return 1;//正數
else if(o1>o2) return -1;//負數
else return 0;
//升序:與上面相反
}
案例(重要,注意看)
import java.util.*; import java.util.Arrays; import java.util.Comparator; class cmp implements Comparator<Double>{ /** *<>內是比較的資料型別(封裝類/自定義類) *如何不寫<...>則下面改成: ** public int compare((Object o1,(Object o2) {//Object ** Double n1=(Double)o1; //強制轉化為比較的資料型別 ** Double n2=(Double)o2; //強制轉化為比較的資料型別 ** } */ public int compare(Double o1,Double o2) { if(o1<o2) return 1; else if(o1>o2) return -1; else return 0; } } public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); Double[] a=new Double[5];//封裝類陣列/自定義類陣列 for(int i=0;i<5;i++) { a[i]=sc.nextDouble(); } Arrays.sort(a, new cmp());//比較 for (double t:a) { System.out.print(t+ " "); } System.out.println(); sc.close(); } }
自定義類陣列排序
方法:同上面從大到小排序
舉例:
/* 要求按照槍支的攻擊力排序(由大到小), 如果某些槍的攻擊力相同則對這些槍按照價格排序(由小到大), 如果某些槍的價格相同則對這些槍按照名字的字典序排列。 (本題中若字串a,b滿足 strcmp(a, b)<0 即滿足字典序) */ import java.util.Arrays; import java.util.Comparator; import java.util.Scanner; import java.util.*; class shu /// 建立類 { String name; int mon; int hunt; } class cmp implements Comparator<shu> { public int compare(shu A, shu B) { if (A.hunt == B.hunt) { if (A.mon == B.mon) {/************** 按字典序排序*****************/ int flag = (A.name).compareTo(B.name); if (flag == 0) return 0; else if (flag < 0) return -1; else return 1; } else { if (A.mon == B.mon) return 0; else if (A.mon < B.mon) return -1; else return 1; } } else { if (A.hunt == B.hunt)return 0; else if (A.hunt < B.hunt) return 1; else return -1; } } } public class Main { public static void main(String[] args) { Scanner sc = new Scanner(System.in); shu num[] = new shu[100005];// 建立類陣列 int n = sc.nextInt(); for (int i = 0; i < n; i++) { num[i] = new shu();// 注意這裡 num[i].name = sc.next(); num[i].hunt = sc.nextInt(); num[i].mon = sc.nextInt(); } Arrays.sort(num, 0, n, new cmp());// 排序 for (int i = 0; i < n; i++) { System.out.print(num[i].name + " "); } sc.close(); } }