MATLAB Answers

Stop value in loop for repeating

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Pallav Patel
Pallav Patel on 12 Mar 2020
Commented: James Tursa on 12 Mar 2020
clc;
clear;
close all;
rng('shuffle');
myint = randi([4,100]);
while mod(myint,2) ~= 0
myint = randi([4,100]);
end
fprintf('%d is the sum of these prime numbers\n',myint);
myprime = primes(myint);
mylength = ceil(length(myprime)/2);
for i=1:length(myprime)
for k=1:length(myprime)
if(myprime(i)+myprime(k)== myint)
num1 = myprime(i);
num2 = myprime(k);
fprintf('%d = %d + %d \n',myint,num1,num2)
end
end
end
i am trying to create the goldbach conjecture but I do not want the prime numbers that have already been listed to repeat. eg 7+5 and 5+7.

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Accepted Answer

James Tursa
James Tursa on 12 Mar 2020
Not sure if you need the numbers to be different or not. Either this:
for k=i:length(myprime)
or this
for k=i+1:length(myprime)

  2 Comments

Pallav Patel
Pallav Patel on 12 Mar 2020
Thank you james. Both of them work perfectly. Could you please elaborate more as I am trying to understand the code
James Tursa
James Tursa on 12 Mar 2020
This simply forces myprime(k) to be greater than (or equal to depending on which code you use) the value of myprime(i). So you will never get both the 5 + 7 and the 7 + 5 choices.

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