站在巨人的肩膀上! 善用 STL 的 sort( ) 與 java.util.Arrays.sort( ); ㄟ .. 這些我說過很多次了喔 .. 概念就是善用別人已經寫好的程式庫啦! C++ STL 整個是女共匪寫的, 裡面一堆與資料結構有關的, 以及一些好用的排序函數 sort( ); 阿那個 Java 就全部抄過來放在 java.util.* 這 package 內 ! 其中排序函數放在 java.util.Arrays 與 java.util.Collections 這兩個類別, 用法上很類似, 觀念也類似, 但是文法不太一樣! 現在我把這兩個最基本的範例 sortAry.java 與 sortAry.cpp 再公佈給大家研究! 注意 Java 不能有獨立存在的 function ! 所以無法寫獨立使用的比較函數 (compare function)! 請把 sortRec.jar 抓回去解壓縮就可看到各原始碼! 注意, sortRec.jar 也是可以執行喔: java -jar sortRec.jar 點這抓 sortRec.jar
01 //sortAry.java -- CopyLeft by tsaiwn@csie.nctu.edu.tw 02 //use Arrays.sort( ) to sort an array of some Object 03 //Note java.lang.Comparable, java.util.Comparator 04 import java.util.*; 05 class sortAry { 06 java.io.PrintStream cout = System.out; 07 public static void main(String xx[ ]) { 08 new sortAry( ); 09 } 10 public sortAry( ) { main( ); } // constructor ; call int main( ); 11 int main( ) { 12 String n[ ]={"abc", "bbs", "aaaaa", "cat", "hat", "dog", "god"}; 13 int ht[ ] = { 168, 158, 180, 175, 173, 165, 163 }; 14 double wt[ ] = { 88.5, 75, 76.5, 66, 68, 70, 60, 99, 33}; 15 ST s[ ] = new ST[7]; 16 for(int i=0; i<7; ++i) 17 s[i] = new ST(n[i], ht[i], wt[i]); // name, height, weight 18 cout.printf("Original s: \n"); print(s); 19 Arrays.sort(s); 20 cout.println("\nafter Arrays.sort(s);: "); print(s); 21 God arben = new God( ); // arben is a Comparator 22 Arrays.sort(s, arben); 23 cout.println("after Arrays.sort(s, arben);: "); print(s); 24 Arrays.sort(s, Collections.reverseOrder(arben)); 25 cout.print("after Arrays.sort(s, "); 26 cout.println("Collections.reverseOrder(arben)); : "); 27 print(s); 28 //Java can NOT pass a compare function to sort program 29 return 0; 30 }// int main( ) 31 void print(ST x[ ]) { // print array of ST, 但故意少印兩個元素 32 cout.print(" "+x[0].name+" "+x[0].height+" "+x[0].wet); 33 for(int i=1; i < x.length-2; ++i) 34 cout.print(", "+x[i].name+" "+x[i].height+" "+x[i].wet); 35 cout.println( ); 36 }//print(ST 37 }//class 38 class ST implements Comparable { 39 ST(String a, int b, double c) { 40 name=a; height=b; wet=c; 41 } 42 public int compareTo(Object bb) { 43 ST b = (ST)bb; System.out.print(". "); 44 return this.height - b.height; 45 } 46 String name; int height; double wet; 47 }//ST 48 class God implements Comparator <ST>{ // God 是比較器類別 49 public int compare(ST aa, ST bb){ 50 if( aa.wet == bb.wet) return 0; 51 if( aa.wet > bb.wet) return -1; // Descending on wet 52 return 1; 53 } 54 }//class God 55 /********************* 56 D:\COURSE\OOP\ppnt> javac sortAry.java 57 58 D:\COURSE\OOP\ppnt> java sortAry 59 Original s: 60 abc 168 88.5, bbs 158 75.0, aaaaa 180 76.5, cat 175 66.0, hat 173 68.0 61 . . . . . . . . . . . . . . . 62 after Arrays.sort(s);: 63 bbs 158 75.0, god 163 60.0, dog 165 70.0, abc 168 88.5, hat 173 68.0 64 after Arrays.sort(s, arben);: 65 abc 168 88.5, aaaaa 180 76.5, bbs 158 75.0, dog 165 70.0, hat 173 68.0 66 after Arrays.sort(s, Collections.reverseOrder(arben)); : 67 god 163 60.0, cat 175 66.0, hat 173 68.0, dog 165 70.0, bbs 158 75.0 68 *************************/

這是 C++ 範例, 使用女共匪寫的 STL 程式庫 ... 01 //sortAry.cpp -- by tsaiwn@csie.nctu.edu.tw 02 //use sort( ) in <algorithm> to sort an array of some Object 03 #include <algorithm> 04 #include <string> 05 #include <iostream> 06 #include <stdio.h> 07 using namespace std; 08 class ST { public: 09 ST( ) { name="Unknown"; } 10 ST(string a, int b, double c) { 11 name=a; height=b; wet=c; 12 } 13 bool operator< (const ST& b) const { // Java: int compareTo( 14 cout<<". "; 15 return this->height < b.height; // Ascending on height 16 } 17 string name; int height; double wet; 18 };//ST 19 class God { public: // 這 God 是個比較器類別 20 bool operator( ) (const ST& aa, const ST& bb){ 21 return aa.wet > bb.wet; // Descending on wet 22 } 23 };//class God 24 void print(ST x[ ], int n) { // print array of ST, 但故意少印兩個元素 25 cout <<" "<<x[0].name<<" "<<x[0].height<<" "<<x[0].wet; 26 for(int i=1; i < n-2; ++i) 27 cout <<", "<<x[i].name<<" "<<x[i].height<<" "<<x[i].wet; 28 cout << endl; 29 }//print(ST 30 bool compf(const ST& aa, const ST& bb){ 31 return aa.wet < bb.wet; // Ascending on wet 32 } 33 int main( ) { 34 string n[ ]={"abc", "bbs", "aaaaa", "cat", "hat", "dog", "god"}; 35 int ht[ ] = { 168, 158, 180, 175, 173, 165, 163 }; 36 double wt[ ] = { 88.5, 75, 76.5, 66, 68, 70, 60, 99, 33}; 37 ST s[7]; // Java: ST s[ ] = new ST[7]; 38 for(int i=0; i<7; ++i) 39 s[i] = * (new ST(n[i], ht[i], wt[i])); // name, height, weight 40 cout << "Original s: " <<endl; 41 print(s, sizeof s/sizeof s[0]); 42 sort(s, s+(sizeof s/sizeof s[0])); 43 cout << "\nafter sort(s, s+sizeof s/sizeof s[0]); : " <<endl; 44 print(s, sizeof s/sizeof s[0]); 45 God arben; // arben is a Comparator 46 sort(s, s+(sizeof s/sizeof s[0]), arben); 47 cout << "after sort with arben: "<< endl; 48 print(s, sizeof s/sizeof s[0]); 49 sort(s, s+(sizeof s/sizeof s[0]), compf); 50 cout << "after sort with compf: "<< endl; 51 // Note Java can NOT pass a compare function to sort program 52 print(s, sizeof s/sizeof s[0]); 53 return 0; 54 }// int main( ) 55 /********************* 56 C:\testc\STL> g++ sortAry.cpp 57 58 C:\testc\STL> a 59 Original s: 60 abc 168 88.5, bbs 158 75, aaaaa 180 76.5, cat 175 66, hat 173 68 61 . . . . . . . . . . . . . . . . . . . . . . . 62 after sort(s, s+sizeof s/sizeof s[0]); : 63 bbs 158 75, god 163 60, dog 165 70, abc 168 88.5, hat 173 68 64 after sort with arben: 65 abc 168 88.5, aaaaa 180 76.5, bbs 158 75, dog 165 70, hat 173 68 66 after sort with compf: 67 god 163 60, cat 175 66, hat 173 68, dog 165 70, bbs 158 75 68 *************************/

點這抓 sortRec.jar