[Huawei 067] 24 point game algorithm

Title Description:

Give 4 numbers of 1-10. By adding, subtracting, multiplying and dividing, you can get a number of 24 and win
Input:
Four 1-10 numbers. [the number is allowed to be repeated, but each number is only allowed to be used once, and the test case guarantees no abnormal number]
Output:
true or false

Java implementation:

```import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
public static void main(String[] args) throws Exception {
Scanner sc = new Scanner(System.in);
while (sc.hasNext()) {
String line = sc.nextLine();
String[] strs = line.split(" ");
List<Integer> list = new ArrayList<Integer>();
for (int i = 0; i < 4; i++) {
}
boolean flag = fun(list);
System.out.println(flag);
}
}

public static boolean fun(List<Integer> list) {
for (int i = 0; i < list.size(); i++) {
int temp = list.get(i);
list.remove(i);
if (getResult(list, temp)) {
return true;
}
}
return false;
}

public static boolean getResult(List<Integer> list, int temp) {
if (list.size() > 0) {
for (int i = 0; i < list.size(); i++) {
int n = list.get(i);
list.remove(i);
if (getResult(list, temp * n) || getResult(list, temp + n) || getResult(list, temp - n)) {
return true;
} else if (temp % n == 0) {
if (getResult(list, temp / n)) {
return true;
}
}
}
return false;
} else {
if (temp == 24) {
return true;
} else {
return false;
}
}
}
}

```

Knowledge points:

• DFS depth first searches, determines an operator and keeps using it until it finally returns false or true
• After removing an element from the list, if it is not found after a deep search, add it back

Tags: Java

Posted on Sun, 09 Feb 2020 15:15:56 -0500 by BlaineSch