Add solution for problem 206

problem-206.c

@@ -0,0 +1,38 @@
+#include <stdio.h>
+
+#define	TRUE	1
+#define	FALSE	0
+
+#define	MIN_NUM	1020304050607080900
+#define MAX_NUM 1929394959697989990
+
+int digits[10] = {0, 9, 8, 7, 6, 5, 4, 3, 2, 1};
+
+int check(long num) {
+	int rem;
+	int i = 0;
+
+	while (num>0) {
+		rem = num % 10;
+		if (rem != digits[i])
+			return FALSE;
+		num /= 100;
+		i++;
+	}
+
+	return TRUE;
+}
+
+
+int main(int argc, char **argv) {
+	long i = 1;
+
+	while ((i*i) < MIN_NUM) i++;
+	while ((i*i) < MAX_NUM) {
+		if (check(i*i))
+			break;
+		i++;
+	}
+	printf("The unique integer is %ld and it's square is %ld\n", i, i*i);
+	return 0;
+}