Is there any way to avoid nested "for" loops in java

Question

so I'm solving a coding challenge and my code failed in test cases with large number of inputs due to timeout.

I need to do a simulation of "count" times. each simulation will produce a random number between 0 and 364 of "size" times each number should be stored and counted if two numbers are stored in the same index that mean the count is '2' then Hits++ return the percentage of hits with respect to "count"

public double calculate(int size, int count) {
        // TODO -- add your code here
        int Hits=0;
        for(int j=1;j<=count;j++) {        // number of simulation 

            int BirthDays[]=new int[365];
            Random rnd = new Random();
            rnd.setSeed(j);

            for(int i=0;i<size;i++){      //number of people  
                int x=rnd.nextInt(365);
                BirthDays[x]=BirthDays[x]+1;
                if(BirthDays[x]>=2){
                    Hits++;
                    break;
                }
            }

        }
        return(((float)Hits/count)*100);

    }

so is there any way to reduce the time complexity ? the data structure can be changed it is not exclusive to arrays .

Answer 1

The biggest time saver I see immediately is to move Random rnd = new Random() out of the loop. You don't need to create a new instance each time and it is quite slow.

public double calculate(int size, int count) {       
    int max = 365;
    int birthDays[] = new int[max];
    Random rnd = new Random();
    int hits = 0;
    for(int j = 1; j <= count; j++) {
        Arrays.fill(birthDays, 0);
        rnd.setSeed(j);
        for(int i = 0; i < size; i++) {
            int x = rnd.nextInt(max);
            birthDays[x]++;
            if(birthDays[x] >=2 ) {
                hits++;
                break;
            }
        }

    }
    return (hits/count) * 100;

}