initial commit

1 files changed, 41 insertions, 38 deletions

diff --git a/main.c b/main.c
index b9bebbb..607d1b2 100644
--- a/main.c
+++ b/main.c
@@ -1,56 +1,59 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <time.h>
-
-#define _USE_MATH_DEFINES
 #include <math.h>
 
-struct point {
-	float x, y;
-};
-
-struct circle {
-	// center not needed for this task
-	/*struct point center;*/
-	float rad;
-};
+#define GEN_MAX 1000000
 
-char in_circle(const struct circle *c, const struct point p) {
-	/*p.x -= c->x;*/
-	/*p.y -= c->y;*/
-	return p.x * p.x + p.y * p.y < c->rad*c->rad;
+static int tenpow(int pow) {
+	int base = 10;
+	int ret = 1;
+	while (pow) {
+		if (pow & 0b1)
+			ret *= base;
+		base *= base;
+		pow >>= 1;
+	}
+	return ret;
 }
 
-float calculate_pi(int iterations) {
-	int in = 0, out = 0;
-	int *arr[2] = {&out, &in};
-	const struct circle c = {.rad = 1.0f};
-	for (int i = 0; i < iterations; ++i) {
-		struct point p = {
-			.x = rand() % 2000000u / 1e6f - 1,
-			.y = rand() % 2000000u / 1e6f - 1
-		};
-		++*arr[in_circle(&c, p)];
-	}
-	return (float)in/iterations * 4;
+static char get_at_pos(unsigned int n, int pos) {
+	n /= tenpow(pos);
+	return n % 10;
 }
 
 int main(int argc, char *argv[]) {
 	srand(time(NULL));
-	int iters;
-	if (argc == 2) {
+	int arr[10] = {0};
+	unsigned int gen;
+
+	int iters, pos;
+	if (argc == 3) {
 		iters = atoi(argv[1]);
+		pos = atoi(argv[2]);
+		if (!iters || !pos) goto fail;
 	} else {
 		fputs("Iterations: ", stdout);
-		if (!scanf("%i", &iters)) {
-			fputs("Input a valid number\n", stderr);
-			return EXIT_FAILURE;
-		}
+		if (!scanf("%i", &iters)) goto fail;
+		fputs("Position (10^N): ", stdout);
+		if (!scanf("%i", &pos)) goto fail;
 	}
-	float pi = calculate_pi(iters);
-	float err = fabs(M_PI-pi)/M_PI;
-	printf(	"calculated pi: %.4f, actual pi: %.4f\n"
-		"error: %.2f%%\n",
-		pi, M_PI, err * 100);
+
+	for (int _ = 0; _ < iters; ++_) {
+		gen = rand() % GEN_MAX;
+#ifdef PRINT_GENERATED
+		printf("%i\n", gen);
+#endif
+		++arr[get_at_pos(gen, pos)];
+	}
+	
+	printf("count of numbers at position %i:\n", pos);
+	for (int i = 0; i < 10; ++i) 
+		printf("\t%i: %i\n", i, arr[i]);
+
 	return EXIT_SUCCESS;
+fail:
+	fputs("Input a valid number\n", stderr);
+	return EXIT_FAILURE;
 }
+