From f61727af1e0ee0e3f42fb10213edd11083bba658 Mon Sep 17 00:00:00 2001
From: eat-swap <root@eatswap.org>
Date: Mon, 25 Apr 2022 23:37:53 +0800
Subject: [PATCH] add: 220425-CN [cpp]

---
 cpp/2204/220425-CN.cpp  | 31 +++++++++++++++++++++++++++++++
 cpp/2204/CMakeLists.txt |  2 +-
 2 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 cpp/2204/220425-CN.cpp

diff --git a/cpp/2204/220425-CN.cpp b/cpp/2204/220425-CN.cpp
new file mode 100644
index 0000000..c79245d
--- /dev/null
+++ b/cpp/2204/220425-CN.cpp
@@ -0,0 +1,31 @@
+#include <vector>
+#include <random>
+#include <ctime>
+#include <unordered_map>
+
+/**
+ * 398. Random Pick Index
+ * Given an integer array nums with possible duplicates, randomly output the index of a given target number. You can assume that the given target number must exist in the array.
+ * Implement the Solution class:
+ * Solution(int[] nums) Initializes the object with the array nums.
+ * int pick(int target) Picks a random index i from nums where nums[i] == target. If there are multiple valid i's, then each index should have an equal probability of returning.
+ */
+
+class Solution {
+private:
+	std::unordered_map<int, std::vector<int>> m;
+
+	std::mt19937 r;
+
+public:
+	explicit Solution(const std::vector<int>& nums) : r(std::time(nullptr)) {
+		auto x = nums.size();
+		while (x--) {
+			m[nums[x]].push_back(x);
+		}
+	}
+
+	int pick(int target) {
+		return m[target][r() % m[target].size()];
+	}
+};
diff --git a/cpp/2204/CMakeLists.txt b/cpp/2204/CMakeLists.txt
index baa8a41..813ae3c 100644
--- a/cpp/2204/CMakeLists.txt
+++ b/cpp/2204/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2204)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2204 220425.cpp)
+ADD_EXECUTABLE(2204 220425-CN.cpp)