Given a random number function of 1 to n, generating a random number of 1 to M of __ function

Given a function that randomly generates integers 1 through n, a function (M > N) that can randomly generate integers 1 to M is written.

Set n = 5, M = 7
The key is to have the same probability of generating 1 to 7 of the number. Call N-time given function, generate n 1 to 5
, select the maximum number of positions until the last one is left. Such as:
Initial 7 numbers [1, 2, 3, 4, 5, 6, 7].
(1) 7 random numbers of 1 to 5, such as [5, 3, 1, 4, 2, 5, 5];
(2) The maximum number (5 at this time) appears in the 1,6,7. So select [1,6,7] (the next step is to have the three
Number, until one of the remaining ones is available;
(3) 3 random numbers of 1 to 5, such as [2,4,1];
(4) The maximum number (4 at this point) appears at 2, so select [6]
At this point 6 is the number of random numbers that occur between 1-7.

The code is as follows:

int getrandm (int m)
{
    int rands[m + 1], Index[m + 1], result[m + 1];
    int I, count;
    for (i = 1; I <= m i++)
        rands[i] = Getrandn ();

    Count = m;
    Count = Indexofmaxnumber (Rands, index, count);
    for (i = 1; I <= count; i++)
        result[i] = index[i];

    Do {for
        (i = 1; I <= count; i++) 
            rands[i] = Getrandn ();
        Count = Indexofmaxnumber (Rands, index, count);
        for (i = 1; I <= count; i++)
            result[i] = result[index[i]];, while
    (Count > 1);
    return result[1];

The random functions that produce 1 to n are as follows:

int Getrandn ()
{
//  Srand ((unsigned) time (NULL));/* Random seed */return  
    rand ()% N + 1;
}

The function of finding the maximum number position in a sequence of random numbers is as follows:

int indexofmaxnumber (int rands[], int index[], int count)
{
    int i, Max, Countmax;
    for (max = rands[1], i = 2; I <= count; i++)
        if (Rands[i] > Max)
            max = rands[i];
    for (Countmax = 0, i = 1; I <= count; i++)
        if (max = = Rands[i])
            Index[++countmax] = i;
    return countmax;
}

The test code is as follows:

#include <stdio.h>                                                                             
#include <stdlib.h>
#include <time.h>

#define N 5

int Getrandn ();
int indexofmaxnumber (int rands[], int index[], int count);
int getrandm (int m);
int main (void) 
{
    srand ((unsigned) time (NULL))/* Random seed */
    /n = rand ()% (Y-x + 1) + X;/*n to x~y between random numbers */
  int i;
    for (i = 0; i < i++)
        printf ("%d", GETRANDM (7));
    printf ("\ n");
    return 0;
}

Output:

The following is the implementation of Java code:

Import Java.util.Random;
    public class Randmfromrandn {private static Random Rand = new Random ();
    private final int n;
    public Randmfromrandn (int n) {THIS.N = n;
    public int Getrandn () {return Rand.nextint (n) + 1;

        public int indexofmaxnumber (int[] rands, int[] index, int count) {int Max, Countmax;
        max = rands[1];

        for (int i = 2; I <= count; i++) if (Rands[i] > max) max = rands[i];
        Countmax = 0;
        for (int i = 1; I <= count; i++) if (rands[i] = max) Index[++countmax] = i;
                
    return Countmax;
        public int getrandm (int m) {int[] Rands = new Int[m + 1];
        int[] Index = new int[m + 1];
        Int[] result = new Int[m + 1];

        int count;
      for (int i = 1; I <= m i++) rands[i] = Getrandn ();  
        Count = m;
        Count = Indexofmaxnumber (Rands, index, count);

        for (int i = 1; I <= count; i++) result[i] = Index[i];
            do {for (int i = 1; I <= count; i++) Rands[i] = Getrandn ();
            Count = Indexofmaxnumber (Rands, index, count);
        for (int i = 1; I <= count; i++) result[i] = result[index[i]];
        while (Count > 1);
    return result[1];
        public static void Main (string[] args) {randmfromrandn nm = new Randmfromrandn (5);
        for (int i = 1; I <= i++) System.out.print (NM.GETRANDM (7) + "");
    System.out.println ();  }
}

Output: