Merge pull request #88883 from joaoh82/add-weighted-random-method

Add `RandomNumberGenerator::rand_weighted` method

1 files changed, 21 insertions, 0 deletions

diff --git a/core/math/random_pcg.cpp b/core/math/random_pcg.cpp
index 45a9285ddd..e754a34271 100644
--- a/core/math/random_pcg.cpp
+++ b/core/math/random_pcg.cpp
@@ -31,6 +31,7 @@
 #include "random_pcg.h"
 
 #include "core/os/os.h"
+#include "core/templates/vector.h"
 
 RandomPCG::RandomPCG(uint64_t p_seed, uint64_t p_inc) :
 		pcg(),
@@ -42,6 +43,26 @@ void RandomPCG::randomize() {
 	seed(((uint64_t)OS::get_singleton()->get_unix_time() + OS::get_singleton()->get_ticks_usec()) * pcg.state + PCG_DEFAULT_INC_64);
 }
 
+int RandomPCG::rand_weighted(const Vector<float> &p_weights) {
+	ERR_FAIL_COND_V_MSG(p_weights.is_empty(), -1, "Weights array is empty.");
+	int64_t weights_size = p_weights.size();
+	const float *weights = p_weights.ptr();
+	float weights_sum = 0.0;
+	for (int64_t i = 0; i < weights_size; ++i) {
+		weights_sum += weights[i];
+	}
+
+	float remaining_distance = Math::randf() * weights_sum;
+	for (int64_t i = 0; i < weights_size; ++i) {
+		remaining_distance -= weights[i];
+		if (remaining_distance < 0) {
+			return i;
+		}
+	}
+
+	return -1;
+}
+
 double RandomPCG::random(double p_from, double p_to) {
 	return randd() * (p_to - p_from) + p_from;
 }