Merge pull request TheAlgorithms#182 from TobCar/master

Add Linear Congruential Generator

Misc/LinearCongruentialGenerator.java

@@ -0,0 +1,57 @@
+/***
+ * A pseudorandom number generator.
+ * 
+ * @author Tobias Carryer
+ * Date: October 10, 2017
+ */
+public class LinearCongruentialGenerator {
+
+    private double a, c, m, previousValue;
+
+    /***
+     * These parameters are saved and used when nextNumber() is called.
+     * The current timestamp in milliseconds is used as the seed.
+     * 
+     * @param multiplier
+     * @param increment
+     * @param modulo The maximum number that can be generated (exclusive). A common value is 2^32.
+     */
+    public LinearCongruentialGenerator( double multiplier, double increment, double modulo ) {
+        this(System.currentTimeMillis(), multiplier, increment, modulo);
+    }
+
+    /***
+     * These parameters are saved and used when nextNumber() is called.
+     * 
+     * @param seed
+     * @param multiplier
+     * @param increment
+     * @param modulo The maximum number that can be generated (exclusive). A common value is 2^32.
+     */
+    public LinearCongruentialGenerator( double seed, double multiplier, double increment, double modulo ) {
+        this.previousValue = seed;
+        this.a = multiplier;
+        this.c = increment;
+        this.m = modulo;
+    }
+
+    /**
+     * The smallest number that can be generated is zero.
+     * The largest number that can be generated is modulo-1. modulo is set in the constructor.
+     * @return a pseudorandom number.
+     */
+    public double nextNumber() {
+        previousValue = (a * previousValue + c) % m;
+        return previousValue;
+    }
+
+    public static void main( String[] args ) {
+        // Show the LCG in action.
+        // Decisive proof that the LCG works could be made by adding each number
+        // generated to a Set while checking for duplicates.
+        LinearCongruentialGenerator lcg = new LinearCongruentialGenerator(1664525, 1013904223, Math.pow(2.0, 32.0));
+        for( int i = 0; i < 512; i++ ) {
+            System.out.println(lcg.nextNumber());
+        }
+    }
+}