generate random numbers of which the sum is constant

Question

I am thinking if there is anyway to generate a set of random numbers of which the sum is always a constant. For example, 20 can be divided into 5 numbers ( 1, 2,3,4,10) I do

Answer 1

yes! try this algorithm

num1=rand()%20;  
num2=rand()%(20-num1);  
num3=rand()%(20-num1-num2);  
num4=rand()%(20-num1-num2-num3);  
num5=20-num4-num3-num2-num1;  

so for sure the five numbers are random and they sum up to 20
[you can do this using loop if you want]

In general you can first randomly generate the number of numbers[n] that will sum up to the number in hand[K]

 n=rand()%k;--assuming the number of rand numbers you want are between 1 and k[sum]
    n1=rand()%k;
    n2=rand()%(k-n1)
    .
    .
    nn-1=rand()%(k-n1...-nn-2)
    nn=k-n1-n2...nn-1

I hope that will help you!