How do I compare integer lists to know which is the largest?

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How do I compare integer lists to know which is the largest?

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#1 by (5 votes)
#2 by (3 votes)

3

I have an algorithm to calculate a sequence of numbers (Collatz Conjecture) .

The problem is that I need all up to 1,000,000 (one million), from there to know what number creates the longest list, I can not think of good ideas, but even if it was so I can not implement them in the code, so how can I know which one? Is the list longer?

If you can give me a serious hand of help, I just want some idea, so that I can solve it, thank you.

This is my code:

public class Collatz14 {


    public static void main(String[] args) {



    }

    public static void pruebaSecuencia(){

        for (int i = 5; i < 1000000; i++) {

            getSequence(i);
        }


    }


    public static int getSequence(int num){

        Vector secuencia = new Vector(10);

        while(num != 1){  //Algoritmo para obtener la secuencia de numeros

        if(num % 2 == 0){

          num = num/2;  
          secuencia.add(num);

        }

        else if(num % 2 != 0){

            num = (num * 3)+ 1;
            secuencia.add(num);
        }
    }

        return secuencia.size(); //Retorno el tamaño de la secuencia
    }


}

java

asked by Romulo Gallegos 12.08.2017 в 22:24

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2 answers

3

You can save the sizes of the vectors in a Map within the function pruebaSecuencia() ,

Map<Integer, Integer> resultados = new HashMap();

public static void pruebaSecuencia(){
    for (int i = 5; i < 1000000; i++) {
        resultados.add(i, getSequence(i));
    }
}

Then you evaluate which is the largest.

Another alternative with the same code that you have can add two variables at the beginning and in the pruebaSecuencia() method you do the validation:

static int numero = 0;
static int tamanioSecuencia = 0;


public static void pruebaSecuencia(){
    for (int i = 5; i < 1000000; i++) {
        int temp = getSequence(i);
        if(temp > tamanioSecuencia){
            tamanioSecuencia = temp;
            numero = i;
        }
     }
 }

Then just print the variables

answered by 13.08.2017 в 00:29

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score 5 · Accepted Answer

Code

public class Main {

    public static void iniciarEjercicio(int limite) {

        /* Secuencia Mayor */
        int numeroMayor = 0;
        int cantidadSecuenciaMayor = 0;

        for (int i = 5; i < limite; i++) {

            int cantidadSecuencia = obtenerSecuencia(i);

            if (cantidadSecuencia > cantidadSecuenciaMayor) {
                numeroMayor = i;
                cantidadSecuenciaMayor = cantidadSecuencia;
            }

        }

        System.out.println("El numero que genera mas secuencia es el " + numeroMayor + " con " + cantidadSecuenciaMayor + " secuencias.");

    }

    public static int obtenerSecuencia(int numero) {

        int contador = 0;

        while (numero != 1) {

            contador++;

            if (numero / 2.0 == numero / 2) {
                numero /= 2;
            } else {
                numero = (3 * numero + 1) / 2;
            }
        }

        return contador;
    }

    public static void main(String[] args) {

        /* Iniciamos el Programa */
        iniciarEjercicio(1000000);

    }
}

Explanation

I have modified your program a bit to make it a little easier, it is not necessary to use arrangements or anything like that, I will explain it to you part by part.

First

We have created the function start obtenerSecuencia() , which receives a number as a parameter and returns the number of numbers found in this sequence.

public static int obtenerSecuencia(int numero) {

    int contador = 0;

    while (numero != 1) {

        contador++;

        if (numero / 2.0 == numero / 2) {
            numero /= 2;
        } else {
            numero = (3 * numero + 1) / 2;
        }
    }

    return contador;
}

See? It only returns an integer variable, whose value is the number of sequences you will find for each numero .

Second

We have created the function iniciarEjercicio() in which the limit to which our program will run will be specified. And in turn contains the algorithm responsible for determining which has been the number that obtained more sequences .

    public static void iniciarEjercicio(int limite) {

        /* Secuencia Mayor */
        int numeroMayor = 0;
        int cantidadSecuenciaMayor = 0;

        for (int i = 5; i < limite; i++) {

            int cantidadSecuencia = obtenerSecuencia(i);

            if (cantidadSecuencia > cantidadSecuenciaMayor) {
                numeroMayor = i;
                cantidadSecuenciaMayor = cantidadSecuencia;
            }

        }

        System.out.println("El numero que genera mas secuencia es el " + numeroMayor + " con " + cantidadSecuenciaMayor + " secuencias.");

    }

Online example!

Note: The online example runs only up to the number 1000, because if you run up to 1 million, it generates slowness in the compiler.

Result

The number that generates the most sequence is 871 with 113 sequences.