diff --git a/README.md b/README.md
index ff3e97a..2f292bf 100644
--- a/README.md
+++ b/README.md
@@ -48,3 +48,20 @@ Implemented are the following Encoders and Decoders:
 * [bose_chaudhuri_hocquenghem_encoder.hh](bose_chaudhuri_hocquenghem_encoder.hh)
 * [bose_chaudhuri_hocquenghem_decoder.hh](bose_chaudhuri_hocquenghem_decoder.hh)
 
+### [exclusive_reduce.hh](exclusive_reduce.hh)
+
+Reduce N times while excluding ith input element
+
+It computes the following, but having only O(N) complexity and using O(1) extra storage:
+
+```
+	output[0] = input[1];
+	output[1] = input[0];
+	for (int i = 2; i < N; ++i)
+		output[i] = op(input[0], input[1]);
+	for (int i = 0; i < N; ++i)
+		for (int j = 2; j < N; ++j)
+			if (i != j)
+				output[i] = op(output[i], input[j]);
+```
+
diff --git a/exclusive_reduce.hh b/exclusive_reduce.hh
new file mode 100644
index 0000000..cfb7151
--- /dev/null
+++ b/exclusive_reduce.hh
@@ -0,0 +1,32 @@
+/*
+Reduce N times while excluding ith input element
+
+Copyright 2018 Ahmet Inan <inan@aicodix.de>
+*/
+
+#ifndef EXCLUSIVE_REDUCE_HH
+#define EXCLUSIVE_REDUCE_HH
+
+namespace CODE {
+
+template <typename TYPE, typename OPERATOR>
+void exclusive_reduce(const TYPE *in, TYPE *out, int N, OPERATOR op)
+{
+	TYPE pre = in[0];
+	for (int i = 1; i < N-1; ++i) {
+		out[i] = pre;
+		pre = op(pre, in[i]);
+	}
+	out[N-1] = pre;
+	TYPE suf = in[N-1];
+	for (int i = N-2; i > 0; --i) {
+		out[i] = op(out[i], suf);
+		suf = op(suf, in[i]);
+	}
+	out[0] = suf;
+}
+
+}
+
+#endif
+