Java Exercises: Find the number of combinations

Java Basic: Exercise-241 with Solution

Write a Java program to find the number of combinations that satisfy p + q + r + s = n where n is a given number <= 4000 and p, q, r, s in the range of 0 to 1000.

Sample Solution:

Java Code:

 import java.util.*;
public class Main{ 
    public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
	System.out.println("Input a positive integer:");
    int[] temp = new int[2001];
    int[] ans = new int[4001];
    for(int i=0;i<=1000;i++){
    for(int j=0;j<=1000;j++){
    temp[i+j]++;
     }
       }
    for(int i=0;i<=2000;i++){
    for(int j=0;j<=2000;j++){
    ans[i+j]+=temp[i]*temp[j];
     }
        }
	      int n = sc.nextInt();
          System.out.println("Number of combinations of a,b,c,d:");
          System.out.println(ans[n]);      
     }
}

Sample Output:

Input a positive integer:
252
Number of combinations of a,b,c,d:
2731135

Flowchart:

Java Code Editor:

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