Exercise: 7

/*
Exercise: 7
01.03.2021
*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main (int argc , char * argv []) {
    long n, i;
    long result = 0;
    char *a = argv [1];
    char str[30];
    int choice;

    if ( argc == 1) {
        while(1){
            printf("Enter 1 to use Brute Force.\n");
            printf("Enter 2 to use Gauss Adder.\n");
            printf("Enter 3 to exit.\n");
            printf("Enter your choice: ");
            scanf("%d", &choice);
            if (choice == 1){
                result = 0;
                printf ( "Please enter Value of n: " );
                scanf ( "%s", str ) ;
                n = strtoul(str, NULL, 10);
                for (i = 1; i <= n; i++){
                    result += i;
                }
                printf("Using a brute force adder, the answer is: %ld.\n", result);
            }
            else if(choice == 2){
                result = 0;
                printf ( "Please enter Value of n: " );
                scanf ( "%s", str ) ;
                n = strtoul(str, NULL, 10);
                result = (n * (n+1))/2;
                printf("Using a gauss adder, the answer is: %ld.\n", result);
            }
            else if (choice == 3){
                break;
            }
            else{
                printf("Enter valid choice.\n");
            }
        }
    }
    else {
        n = strtoul(a, NULL, 10);
    }

}