Data commit

Task/Evolutionary-algorithm/C/evolutionary-algorithm-1.c

@@ -0,0 +1,67 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+const char target[] = "METHINKS IT IS LIKE A WEASEL";
+const char tbl[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ ";
+
+#define CHOICE (sizeof(tbl) - 1)
+#define MUTATE 15
+#define COPIES 30
+
+/* returns random integer from 0 to n - 1 */
+int irand(int n)
+{
+	int r, rand_max = RAND_MAX - (RAND_MAX % n);
+	while((r = rand()) >= rand_max);
+	return r / (rand_max / n);
+}
+
+/* number of different chars between a and b */
+int unfitness(const char *a, const char *b)
+{
+	int i, sum = 0;
+	for (i = 0; a[i]; i++)
+		sum += (a[i] != b[i]);
+	return sum;
+}
+
+/* each char of b has 1/MUTATE chance of differing from a */
+void mutate(const char *a, char *b)
+{
+	int i;
+	for (i = 0; a[i]; i++)
+		b[i] = irand(MUTATE) ? a[i] : tbl[irand(CHOICE)];
+
+	b[i] = '\0';
+}
+
+int main()
+{
+	int i, best_i, unfit, best, iters = 0;
+	char specimen[COPIES][sizeof(target) / sizeof(char)];
+
+	/* init rand string */
+	for (i = 0; target[i]; i++)
+		specimen[0][i] = tbl[irand(CHOICE)];
+	specimen[0][i] = 0;
+
+	do {
+		for (i = 1; i < COPIES; i++)
+			mutate(specimen[0], specimen[i]);
+
+		/* find best fitting string */
+		for (best_i = i = 0; i < COPIES; i++) {
+			unfit = unfitness(target, specimen[i]);
+			if(unfit < best || !i) {
+				best = unfit;
+				best_i = i;
+			}
+		}
+
+		if (best_i) strcpy(specimen[0], specimen[best_i]);
+		printf("iter %d, score %d: %s\n", iters++, best, specimen[0]);
+	} while (best);
+
+	return 0;
+}