Question

How to calculate sum of series 1 + 11 + 111 + 1111 + ... N in Java

Answer 1

// sum = 1 + 11 + 111 + 1111 + ... N 
 
public class MyClass {
    private static int sum_of_series(int N) {
        int sum = 0;
        int tmp = 1;
     
        for (int i = 0; i < N; i++) {
            System.out.print(tmp + " ");

            if (i < N - 1) {
                System.out.print("+ ");
            }
     
            sum += tmp;
            tmp = (tmp * 10) + 1;
        }
     
        return sum;
    }
    public static void main(String args[]) {
        int N = 6;
 
        int sum = sum_of_series(N);
 
        System.out.println("= " + sum);
    }
}

 
 
 
 
/*
run:
      
1 + 11 + 111 + 1111 + 11111 + 111111 = 123456
   
*/

 

 

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