From 4e873f87b0c40e203b1f895dee5f8736ccf7961a Mon Sep 17 00:00:00 2001
From: Matej Focko <me@mfocko.xyz>
Date: Wed, 1 May 2024 00:53:46 +0200
Subject: [PATCH] =?UTF-8?q?cpp:=20add=20=C2=AB1915.=20Number=20of=20Wonder?=
 =?UTF-8?q?ful=20Substrings=C2=BB?=
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Signed-off-by: Matej Focko <me@mfocko.xyz>
---
 cpp/number-of-wonderful-substrings.cpp | 29 ++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 cpp/number-of-wonderful-substrings.cpp

diff --git a/cpp/number-of-wonderful-substrings.cpp b/cpp/number-of-wonderful-substrings.cpp
new file mode 100644
index 0000000..2c2568f
--- /dev/null
+++ b/cpp/number-of-wonderful-substrings.cpp
@@ -0,0 +1,29 @@
+#include <cstdint>
+#include <string>
+#include <unordered_map>
+
+class Solution {
+    static const std::uint32_t BIT = 1;
+
+  public:
+    long long wonderfulSubstrings(const std::string &word) {
+        long long result = 0;
+
+        std::unordered_map<std::uint32_t, long long> freqs;
+        freqs[0] = 1;
+
+        std::uint32_t mask = 0;
+        for (char c : word) {
+            mask ^= BIT << (c - 'a');
+
+            result += freqs[mask];
+            ++freqs[mask];
+
+            for (auto odd_c = 0; odd_c < 10; ++odd_c) {
+                result += freqs[mask ^ (BIT << odd_c)];
+            }
+        }
+
+        return result;
+    }
+};