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Cracking the Coding: Practice Problem
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// ch 8.7 | |
import java.util.*; | |
public class Main { | |
public static void main(String args[]) { | |
System.out.println(getPerms("ab")); // [ab, ba] | |
System.out.println(getPerms("abc")); // [abc, acb, bac, bca, cab, cba] | |
System.out.println(getPerms("love")); // [love, loev, lvoe, lveo, leov, levo, olve, olev, ovle, ovel, oelv, oevl, vloe, vleo, vole, voel, velo, veol, elov, elvo, eolv, eovl, evlo, evol] | |
} | |
static ArrayList < String > getPerms(String input) { | |
ArrayList < String > perms = new ArrayList < > (); | |
if (input.length() == 0) { | |
perms.add(input); | |
} else { | |
for (int i = 0; i < input.length(); i++) { | |
ArrayList < String > sub = getPerms(input.substring(0, i) + input.substring(i + 1, input.length())); | |
for (String s: sub) { | |
perms.add(input.charAt(i) + s); | |
} | |
} | |
} | |
return perms; | |
} | |
} | |
// ch 8.13 | |
import java.util.*; | |
public class Main { | |
public static void main(String args[]) { | |
System.out.println("Hello"); | |
ArrayList<Box> boxes = new ArrayList<>(); | |
boxes.add(new Box(1, 1, 1)); | |
boxes.add(new Box(2, 2, 2)); | |
boxes.add(new Box(3, 3, 3)); | |
System.out.println(createStack(boxes)); // 6 | |
boxes.add(new Box(3, 4, 3)); | |
System.out.println(createStack(boxes)); // 7 | |
boxes.add(new Box(6, 4, 4)); | |
boxes.add(new Box(7, 5, 5)); | |
boxes.add(new Box(7, 7, 7)); | |
System.out.println(createStack(boxes)); // 17 | |
} | |
static class Box implements Comparable<Box> { | |
int w, h, d; | |
Box(int w, int h, int d) { | |
this.w = w; | |
this.h = h; | |
this.d = d; | |
} | |
public int compareTo(Box b) { | |
if (this.w < b.w && this.h < b.h && this.d < b.d) return -1; | |
if (this.w > b.w && this.h > b.h && this.d > b.d) return 1; | |
return 0; | |
} | |
} | |
static int createStack(ArrayList<Box> boxes) { | |
int maxheight = 0; | |
for (Box b: boxes) | |
maxheight = Math.max(maxheight, createStack(b, boxes)); | |
return maxheight; | |
} | |
static int createStack(Box bottom, ArrayList<Box> boxes) { | |
int maxheight = 0; | |
for (Box b: boxes) | |
if (bottom.compareTo(b) > 0) | |
maxheight = Math.max(maxheight, createStack(b, boxes)); | |
return bottom.h + maxheight; | |
} | |
} | |
// ch 13.8 | |
import java.util.*; | |
import java.util.stream.*; | |
public class Main { | |
public static void main(String args[]) { | |
List<Integer> list = new ArrayList<>(); | |
list.add(1); | |
list.add(2); | |
list.add(3); | |
list.add(4); | |
list.add(5); | |
System.out.println(getRandomSubset(list)); | |
} | |
static List<Integer> getRandomSubset(List<Integer> list) { | |
Random random = new Random(); | |
return list.stream().filter(k -> random.nextBoolean()) | |
.collect(Collectors.toList()); | |
} | |
} | |
// 16.7: Number Max | |
import java.util.*; | |
public class Main { | |
public static void main(String args[]) { | |
System.out.println(getMax(10000, 10001)); // 10001 | |
} | |
static int getMax(int a, int b) { | |
int sum = a + b; | |
int dff = Math.abs(a - b); | |
int min = (sum - dff) / 2; | |
return sum - min; | |
} | |
} |
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