Write a function that generates one of 3 numbers according to given probabilities

You are given a function rand(a, b) which generates equiprobable random numbers between [a, b] inclusive. Generate 3 numbers x, y, z with probability P(x), P(y), P(z) such that P(x) + P(y) + P(z) = 1 using the given rand(a,b) function.

The idea is to utilize the equiprobable feature of the rand(a,b) provided. Let the given probabilities be in percentage form, for example P(x)=40%, P(y)=25%, P(z)=35%..

 1 // This function generates 'x' with probability px/100, 'y' with 
 2 // probability py/100  and 'z' with probability pz/100:
 3 // Assumption: px + py + pz = 100 where px, py and pz lie 
 4 // between 0 to 100 
 5 int random(int x, int y, int z, int px, int py, int pz) {       
 6         // Generate a number from 1 to 100
 7         int r = rand(1, 100);
 8       
 9         // r is smaller than px with probability px/100
10         if (r <= px)
11             return x;
12  
13          // r is greater than px and smaller than or equal to px+py 
14          // with probability py/100 
15         if (r <= (px+py))
16             return y;
17  
18          // r is greater than px+py and smaller than or equal to 100 
19          // with probability pz/100 
20         else
21             return z;
22 }

 

posted @ 2014-06-05 19:50  linyx  阅读(154)  评论(0)  编辑  收藏  举报