Data commit

Task/Dice-game-probabilities/C/dice-game-probabilities.c

@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <stdint.h>
+
+typedef uint32_t uint;
+typedef uint64_t ulong;
+
+ulong ipow(const uint x, const uint y) {
+    ulong result = 1;
+    for (uint i = 1; i <= y; i++)
+        result *= x;
+    return result;
+}
+
+uint min(const uint x, const uint y) {
+    return (x < y) ? x : y;
+}
+
+void throw_die(const uint n_sides, const uint n_dice, const uint s, uint counts[]) {
+    if (n_dice == 0) {
+        counts[s]++;
+        return;
+    }
+
+    for (uint i = 1; i < n_sides + 1; i++)
+        throw_die(n_sides, n_dice - 1, s + i, counts);
+}
+
+double beating_probability(const uint n_sides1, const uint n_dice1,
+                           const uint n_sides2, const uint n_dice2) {
+    const uint len1 = (n_sides1 + 1) * n_dice1;
+    uint C1[len1];
+    for (uint i = 0; i < len1; i++)
+        C1[i] = 0;
+    throw_die(n_sides1, n_dice1, 0, C1);
+
+    const uint len2 = (n_sides2 + 1) * n_dice2;
+    uint C2[len2];
+    for (uint j = 0; j < len2; j++)
+        C2[j] = 0;
+    throw_die(n_sides2, n_dice2, 0, C2);
+
+    const double p12 = (double)(ipow(n_sides1, n_dice1) * ipow(n_sides2, n_dice2));
+
+    double tot = 0;
+    for (uint i = 0; i < len1; i++)
+        for (uint j = 0; j < min(i, len2); j++)
+            tot += (double)C1[i] * C2[j] / p12;
+    return tot;
+}
+
+int main() {
+    printf("%1.16f\n", beating_probability(4, 9, 6, 6));
+    printf("%1.16f\n", beating_probability(10, 5, 7, 6));
+    return 0;
+}