Chapter 13 - Searching and Sorting

Chapter 13 - Searching and Sorting - &KDSWHU 6HDUFKLQJ...

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"); Scanner console = new Scanner(System.in); String word = console.nextLine(); int index = words.indexOf(word); if (index >= 0) { System.out.println(word + " is word #" + index + " in the book."); } else { System.out.println(word + " isn't found in the book."); }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guess = 50 ^ incorrect. hint: higher 0 10 20 30 40 guess = 75 incorrect. hint: lower 50 60 70 80 DQG 90 100 60 70 ^ 80 90 100 0 10 20 30 40 50 guess = 62 incorrect. hint: higher 0 10 20 30 40 50 guess = 69 incorrect. hint: higher 0 10 20 30 40 guess = 72 incorrect. hint: lower 0 10 20 guess = 71 correct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demonstrate the Arrays.binarySearch method String strings = {"a", "b", "c", "d", "e", "f", "g", "h"}; int index = Arrays.binarySearch(strings, "e"); // 4 System.out.println("e is found at index " + index); ,I \RX UH XVLQJ D OLVW VXFK DV DQ $UUD\/LVW LQVWHDG &ROOHFWLRQV ELQDU\6HDUFK WR VHDUFK WKH OLVW RI HOHPHQWV \RX FDQ FDOO WKH VWDWLF PHWKRG String strings = {"a", "b", "c", "d", "e", "f", "g", "h"}; ArrayList<String> list = new ArrayList<String>(); for (String s : strings) { list.add(s); } // demonstrate the Collections.binarySearch method int index = Collections.binarySearch(list, "e"); // 4 System.out.println("e is found at index " + index); ,Q WKH FDVH RI DUUD\V RU OLVWV WKH GDWD PXVW EH LQ VRUWHG RUGHU WR XVH WKH ELQDU\6HDUFK PHWKRG EHFDXVH LW UHOLHV RQ WKH VRUWHGQHVV WR PRUH TXLFNO\ ILQG WKH WDUJHW YDOXH ,I \RX FDOO ELQDU\6HDUFK RQ XQVRUWHG GDWD WKH UHVXOWV DUH XQGHILQHG DQG WKH DOJRULWKP GRHVQ W SURPLVH WKDW LW ZLOO UHWXUQ WKH ULJKW DQVZHU 7KH IROORZLQJ SURJUDP GHPRQVWUDWHV D ELQDU\ VHDUFK IRU D ZRUG LQ D GLFWLRQDU\ ILOH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 import java.io.*; import java.util.*; public class FindWords { public static void main(String args) throws FileNotFoundException { Scanner in = new Scanner(new File("words.txt")); ArrayList<String> words = new ArrayList<String>(); while (in.hasNext()) { words.add(in.next()); } System.out.print("Your word? "); Scanner console = new Scanner(System.in); String word = console.nextLine().trim().toLowerCase(); int index = Collections.binarySearch(words, word); if (index >= 0) { System.out.println(word + " is word #" + index + " in the dictionary."); } else { System.out.println(word + " isn't found in the dictionary."); } } } +HUH DUH WZR H[DPSOH UXQV RI WKH SURJUDP DQG WKHLU UHVXOWLQJ RXWSXW Your word? tugboat tugboat is word #159226 in the dictionary. Your word? googlymoogly googlymoogly isn't found in the dictionary. 656 6RUWLQJ 6RUWLQJ LV D YHU\ FRPPRQ DQG LPSRUWDQW FRPSXWLQJ WDVN :KHQ EURZVLQJ \RXU KDUG GULYH \RX PLJKW VRUW \RXU ILOHV E\ ILOHQDPH H[WHQVLRQ DQG GDWH :KHQ SOD\LQJ PXVLF \RX PLJKW VRUW \RXU VRQJV E\ DUWLVW \HDU RU JHQUH :H DOVR VDZ WKDW VRUWHG DUUD\V DQG OLVWV FDQ EH VHDUFKHG YHU\ TXLFNO\ ZLWK WKH ELQDU\ VHDUFK DOJRULWKP 6RUWLQJ IXQFWLRQDOLW\ LV SURYLGHG E\ WKH -DYD FODVV OLEUDULHV IRU DUUD\V DQG OLVWV $Q DUUD\ FDQ EH VRUWHG ZLWK WKH $UUD\V VRUW PHWKRG // demonstrate the Arrays.sort method String strings = {"c", "b", "g", "h", "d", "f", "e", "a"}; Arrays.sort(strings); System.out.println(Arrays.toString(strings)); 7KH SUHFHGLQJ FRGH SURGXFHV WKH IROORZLQJ RXWSXW [a, b, c, d, e, f, g, h] 7KH DUUD\ PXVW EH RI D W\SH WKDW FDQ EH FRPSDUHG WKDW LV RQH WKDW LPSOHPHQWV WKH &RPSDUDEOH LQWHUIDFH )RU H[DPSOH \RX FDQ VRUW DQ DUUD\ RI LQWV RU 6WULQJV EXW \RX FDQ W VRUW DQ DUUD\ RI 3RLQW REMHFWV RU &RORU REMHFWV 7KHUH LV DOVR D PHWKRG QDPHG &ROOHFWLRQV VRUW WKDW DFFHSWV D OLVW VXFK DV DQ $UUD\/LVW DV D SDUDPHWHU DQG SXWV LWV HOHPHQWV LQWR VRUWHG RUGHU 7KH IROORZLQJ FRGH SURGXFHV WKH VDPH RXWSXW // demonstrate the Collections.sort method ArrayList<String> list = new ArrayList<String>(); for (String s : strings) { // uses previous array list.add(s); } Collections.sort(list); System.out.println(list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tring ranks = {"2", "3", "4", "5", "6", "7", "8", "9", "10", "Jack", "Queen", "King", "Ace"}; String suits = {"Clubs", "Diamonds", "Hearts", "Spades"}; ArrayList<String> deck = new ArrayList<String>(); for (String rank : ranks) { for (String suit : suits) { deck.add(rank + " of " + suit); } } Collections.shuffle(deck); System.out.println("Top card = " + deck.get(deck.size() - 1)); 7KH FRGH UDQGRPO\ SURGXFHV RXWSXW VXFK DV WKH IROORZLQJ D GLIIHUHQW RXWSXW RQ HDFK UXQ Top card = 10 of Spades 7KH IROORZLQJ WDEOH EULHIO\ VXPPDUL]HV WKH XVHIXO VWDWLF PHWKRGV LQ -DYD V FODVV OLEUDULHV IRU VHDUFKLQJ VRUWLQJ DQG VKXIIOLQJ 6HDUFKLQJ DQG 6RUWLQJ LQ -DYD V &ODVV /LEUDULHV 0HWKRG Arrays.binarySearch(array) 'HVFULSWLRQ 5HWXUQV WKH LQGH[ RI WKH JLYHQ YDOXH LQ WKH JLYHQ DUUD\ DVVXPLQJ WKDW WKH DUUD\ V HOHPHQWV DUH FXUUHQWO\ LQ VRUWHG RUGHU Arrays.sort(array) $UUDQJHV WKH JLYHQ DUUD\ V HOHPHQWV LQWR VRUWHG RUGHU Collections.binarySearch(list) 5HWXUQV WKH LQGH[ RI WKH JLYHQ YDOXH LQ WKH JLYHQ OLVW DVVXPLQJ WKDW WKH OLVW V HOHPHQWV DUH FXUUHQWO\ LQ VRUWHG RUGHU Collections.shuffle(list) $UUDQJHV WKH JLYHQ OLVW V HOHPHQWV LQWR D UDQGRP RUGHU Collections.sort(list) $UUDQJHV WKH JLYHQ OLVW V HOHPHQWV LQWR VRUWHG RUGHU &XVWRP 2UGHULQJ ZLWK &RPSDUDWRUV 6RPHWLPHV \RX ZDQW WR VHDUFK RU VRUW D FROOHFWLRQ RI REMHFWV LQ DQ RUGHULQJ GLIIHUHQW WKDW WKDW RI LWV &RPSDUDEOH LPSOHPHQWDWLRQ )RU H[DPSOH FRQVLGHU WKH IROORZLQJ FRGH WKDW VRUWV DQ DUUD\ RI 6WULQJV DQG SULQWV WKH UHVXOW String strings = {"Foxtrot", "alpha", "echo", "golf", "bravo", "hotel", "Charlie", "DELTA"}; Arrays.sort(strings); System.out.println(Arrays.toString(strings)); 7KH IROORZLQJ RXWSXW LV SURGXFHG ZKLFK PD\ QRW EH ZKDW \RX H[SHFWHG 658 [Charlie, DELTA, Foxtrot, alpha, bravo, echo, golf, hotel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tring strings = {"Foxtrot", "alpha", "echo", "golf", "bravo", "hotel", "Charlie", "DELTA"}; Arrays.sort(strings, String.CASE_INSENSITIVE_ORDER); System.out.println(Arrays.toString(strings)); 7KH DUUD\ LV RXWSXW LQ WKH IROORZLQJ RUGHU [alpha, bravo, Charlie, DELTA, echo, Foxtrot, golf, hotel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import java.util.*; // Compares String objects by length. public class LengthComparator implements Comparator<String> { public int compare(String s1, String s2) { return s1.length() - s2.length(); } } 1RZ WKDW ZH YH ZULWWHQ D OHQJWK FRPSDUDWRU ZH FDQ SDVV RQH ZKHQ VRUWLQJ DQ DUUD\ RU OLVW RI 6WULQJ REMHFWV 659 Arrays.sort(strings, new LengthComparator()); System.out.println(Arrays.toString(strings)); +HUH V WKH RXWSXW ZKHQ XVHG RQ WKH VDPH 6WULQJ DUUD\ IURP HDUOLHU LQ WKLV VHFWLRQ 1RWLFH WKDW WKH VWULQJV DSSHDU LQ RUGHU RI LQFUHDVLQJ OHQJWK [echo, golf, alpha, bravo, hotel, DELTA, Foxtrot, Charlie] 6RPHWLPHV \RX ZDQW WR VHDUFK RU VRUW D FROOHFWLRQ RI REMHFWV WKDW GRQ W LPSOHPHQW WKH &RPSDUDEOH LQWHUIDFH )RU H[DPSOH WKH 3RLQW FODVV GRHVQ W LPSOHPHQW &RPSDUDEOH EXW \RX PLJKW ZLVK WR VRUW DQ DUUD\ RI 3RLQW REMHFWV E\ [ FRRUGLQDWH EUHDNLQJ WLHV E\ \ FRRUGLQDWH $Q H[DPSOH &RPSDUDWRU WKDW FRPSDUHV 3RLQW REMHFWV LQ WKLV ZD\ LV WKH IROORZLQJ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 import java.awt.*; import java.util.*; // Compares Point objects by x coordinate and then by y coordinate. public class PointComparator implements Comparator<Point> { public int compare(Point p1, Point p2) { int dx = p1.x - p2.x; int dy = p1.y - p2.y; if (dx < 0 || (dx == 0 && dy < 0)) { return -1; } else if (dx > 0 || (dx == 0 && dy > 0)) { return 1; } else { return 0; } } } 7KH IROORZLQJ VKRUWHU YHUVLRQ XVLQJ WKH FRPSDUH7R VXEWUDFWLRQ WULFN DOVR ZRUNV public int compare(Point p1, Point p2) { int dx = p1.x - p2.x; int dy = p1.y - p2.y; if (dx == 0) { return dy; } else { return dx; } } )RU H[DPSOH WKH IROORZLQJ FRGH XVHV RXU 3RLQW&RPSDUDWRU WR VRUW DQ DUUD\ RI IRXU 3RLQW REMHFWV Point points = { new Point(4, -2), new Point(-1, 15), new Point(3, 7), new Point(0, 9) }; Arrays.sort(points, new PointComparator()); $IWHU WKLV FRGH WKH SRLQWV DSSHDU LQ WKH IROORZLQJ RUGHU 660 (-1, 15), (0, 9), (3, 7), (4, -2) 7KH IROORZLQJ WDEOH VXPPDUL]HV VHYHUDO XVHIXO SODFHV &RPSDUDWRUV DSSHDU LQ WKH -DYD FODVV OLEUDULHV 8VHIXO &RPSDUDWRU )XQFWLRQDOLW\ LQ -DYD V &ODVV /LEUDULHV &RPSDUDWRU 0HWKRG Arrays.binarySearch(array, value, comparator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rrays.sort(array, comparator) Collections.binarySearch(list, value, comparator) Collections.max(collection, comparator) Collections.min(collection, comparator) Collections.sort(list, comparator) &RPSDUDWRUV FDQ DOVR EH XVHG ZLWK YDULRXV FROOHFWLRQV WKDW XVH HOHPHQW RUGHULQJ VXFK DV 7UHH6HW RU 3ULRULW\4XHXH 3URJUDP (IILFLHQF\ $V ZH SURJUHVV LQ WKLV WH[WERRN WKH SURJUDPV ZH UH ZULWLQJ DUH JHWWLQJ PRUH FRPSOH[ :H UH DOVR VHHLQJ WKDW WKHUH DUH PDQ\ ZD\V WR VROYH WKH VDPH SUREOHP +RZ GR ZH FRPSDUH GLIIHUHQW VROXWLRQV WR WKH VDPH SUREOHP WR VHH ZKLFK LV EHWWHU" $OVR ZH VD\ WKDW DQ DOJRULWKP WKDW VROYHV D SUREOHP TXLFNO\ DQG FOHYHUO\ LV HIILFLHQW %XW KRZ IDVW LV IDVW HQRXJK" $Q DOJRULWKP WKDW ORRNV XS D ZRUG LQ GLFWLRQDU\ DQG WDNHV PLQXWHV WR UXQ LV SUREDEO\ WRR VORZ %XW DQ DOJRULWKP WKDW UHQGHUV D FRPSOH[ GLPHQVLRQDO DQLPDWLRQ LQ PLQXWHV LV SUREDEO\ YHU\ IDVW 7KH DFFHSWDEOH SHUIRUPDQFH IRU D JLYHQ SURJUDP GHSHQGV RQ ZKDW WKH SURJUDP LV GRLQJ 6R KRZ GR ZH JDXJH FRPSXWLQJ SHUIRUPDQFH" 2QH ZD\ LV WR ZULWH WKH SURJUDP UXQ LW DQG PHDVXUH KRZ ORQJ LW WDNHV WR UXQ 7KLV LV VRPHWLPHV FDOOHG DQ HPSLULFDO DQDO\VLV RI WKH DOJRULWKP )RU H[DPSOH ZKLFK LV WKH IDVWHU SURJUDP WR VHDUFK DQ DUUD\ RQH WKDW VHTXHQWLDOO\ VHDUFKHV IRU WKH GHVLUHG WDUJHW HOHPHQW RU RQH WKDW ILUVW VRUWV WKH DUUD\ WKHQ SHUIRUPV D ELQDU\ VHDUFK RQ WKH VRUWHG DUUD\" :H FRXOG HPSLULFDOO\ DQDO\]H LW E\ ZULWLQJ ERWK SURJUDPV UXQQLQJ WKHP DQG WLPLQJ WKHP WR GHWHUPLQH ZKLFK SHUIRUPV EHWWHU 661 %XW HPSLULFDOO\ DQDO\]LQJ DQ DOJRULWKP LVQ W D YHU\ UHOLDEOH PHDVXUH EHFDXVH RQ D GLIIHUHQW FRPSXWHU ZLWK GLIIHUHQW SURFHVVRU VSHHG DQG PHPRU\ WKH SURJUDP PD\ QRW UXQ LQ WKH VDPH DPRXQW RI WLPH $OVR WR HPSLULFDOO\ WHVW DQ DOJRULWKP ZH PXVW ZULWH LW DQG WLPH LW ZKLFK FDQ EH D FKRUH $ PRUH QHXWUDO ZD\ WR PHDVXUH D SURJUDP V SHUIRUPDQFH LV WR H[DPLQH LWV FRGH RU SVHXGRFRGH DQG FRXQW URXJKO\ KRZ PDQ\ VWDWHPHQWV DUH H[HFXWHG 7KLV LV D OLJKW YHUVLRQ RI ZKDW V FDOOHG DOJRULWKP DQDO\VLV ZKLFK FRQVLVWV R...
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