Übung 4 Luca R.

#include <stdio.h>
#include <math.h>
#include "uebungen.h"

void isHappyNumber();
void berechnePI();
void calculatePrimeFactors();

///Main Methode
int main(){
    /*
     * isHappyNumber();
     * calculatePrimeFactors();
     * berechnePI();
     * */
    return 0;
}



///Aufgabe 1 Fröhliche Zahlen
int getLastDigit(int number);
int removeLastDigit(int number);

void isHappyNumber(){

    for(int i = 1; i <= 500; i++){
        int currentNumber = i;
        int nextNumber = 0;
        while (nextNumber != 1) { //schleife wird solange durchgeführt wie Berechnungsschritt ein Ergebnis ungleich 1 ergibt

            nextNumber = 0;
            while (currentNumber > 0) {
                nextNumber = nextNumber + (getLastDigit(currentNumber) * getLastDigit(currentNumber));
                currentNumber = removeLastDigit(currentNumber);
            }
            currentNumber = nextNumber;
            if(nextNumber == 20){
                break;
            }
        }

        if(nextNumber == 1){
            printf("%d ist eine froehliche Zahl!\n", i);
        }
    }

}

int getLastDigit(int number){
    if(number < 10 && number < 0){
        return number;
    }else{
        return number%10;
    }
}

int removeLastDigit(int number){
    return (number - (number%10))/10;
}

///Aufgabe 2 Berechnung von PI
void berechnePI(){

    double precision;
    printf("Bitte geben Sie die Genauigkeit an (Zahl kleiner eins): ");
    scanf("%lf", &precision);

    double lastResult = 0;
    double currentResult =  1.0  / (2 * 0 + 1); // n = 0

    for (int n = 1; fabs(lastResult - currentResult) >= precision/4; n++) {
        lastResult = currentResult;
        currentResult = currentResult + pow(-1, n%2) * (1.0  / (2 * n + 1));
    }

    double result = 4 * currentResult;
    printf("\nPI berechnet:  %.*lf", 15, result);
    printf("\nPI aus Math.h: %.*lf", 15, M_PI);
    printf("\nDifferenz:     %.*lf", 15, fabs(M_PI - result));
    printf("\nPrecision:     %.*lf", 15, precision);
}


void calculatePrimeFactors(){

    int number;
    printf("Bitte geben sie eine Zahl zur Primfaktorzerlegung an. \n");
    scanf("%d", &number);
    printf("\n");

    int prim[number/2];
    int index = 0;
    int arrayLength = 0;

    for(int i = 2; i <= number/2; i++){
        int j = 2;
        while (i % j != 0 && j < i){
            j++;
        }
        if(j == i){
            prim[index] = i;
            index++;
        }
    }

    arrayLength = index + 1;
    int notPrim = 0;

    for(int i = 0; i < arrayLength; i++){
        while (number % prim[i] == 0){
            number = number / prim[i];
            printf("%d \n", prim[i]);
            notPrim = 1;
        }
    }
    if(notPrim == 0){
        printf("%d", number);
    }
}