Adding a C Monte Carlo implementation. (#121)

* Adding monte_carlo.c

* changing monte_carlo.md

* naming fix for monte_carlo.c

* adding precentage error to monte_carlo.c

* updating monte_carlo.md

Author: Gathros

chapters/monte_carlo/code/c/monte_carlo.c

@@ -0,0 +1,35 @@
+#include <math.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <time.h>
+
+bool in_circle(double x, double y, double radius) {
+    return x * x + y * y < radius * radius;
+}
+
+void monte_carlo(int samples, double radius) {
+    int count = 0;
+
+    for (int i = 0; i < samples; ++i) {
+        double x = (double)rand() * 2.0 / RAND_MAX - 1.0;
+        double y = (double)rand() * 2.0 / RAND_MAX - 1.0;
+
+        if (in_circle(x, y, radius)) {
+            count += 1;
+        }
+    }
+
+    double estimate = 4.0 * count / (samples * radius * radius);
+
+    printf("The estimate of pi is %f\n", estimate);
+    printf("Which has an error of %0.2f%\n", 100 * (M_PI - estimate) / M_PI);
+}
+
+int main() {
+    srand(time(NULL));
+
+    monte_carlo(1000000, 1.0);
+
+    return 0;
+}

chapters/monte_carlo/monte_carlo.md

@@ -39,6 +39,8 @@ each point is tested to see whether it's in the circle or not:
 {% method %}
 {% sample lang="jl" %}
 [import:2-8, lang:"julia"](code/julia/monte_carlo.jl)
+{% sample lang="c" %}
+[import:7-9, lang:"c_cpp"](code/c/monte_carlo.c)
 {% sample lang="hs" %}
 [import:7-7, lang:"haskell"](code/haskell/monteCarlo.hs)
 {% endmethod %}
@@ -75,6 +77,9 @@ Feel free to submit your version via pull request, and thanks for reading!
 {% sample lang="jl" %}
 ### Julia
 [import, lang:"julia"](code/julia/monte_carlo.jl)
+{% sample lang="c" %}
+### C
+[import, lang:"c_cpp"](code/c/monte_carlo.c)
 {% sample lang="hs" %}
 ### Haskell
 [import, lang:"haskell"](code/haskell/monteCarlo.hs)