From e8cba72e591c03c698e7d65bf77dcfbc357b386d Mon Sep 17 00:00:00 2001
From: ndt0208 <ndt0208@users.noreply.github.com>
Date: Mon, 28 Sep 2026 19:04:30 +0700
Subject: [PATCH] feat(cpp): add lru benchmark (1.cpp)

---
 bench/algorithm/lru/1.cpp | 155 ++++++++++++++++++++++++++++++++++++++
 bench/bench_cpp.yaml      |   3 +
 2 files changed, 158 insertions(+)
 create mode 100644 bench/algorithm/lru/1.cpp

diff --git a/bench/algorithm/lru/1.cpp b/bench/algorithm/lru/1.cpp
new file mode 100644
index 000000000..ab649a249
--- /dev/null
+++ b/bench/algorithm/lru/1.cpp
@@ -0,0 +1,155 @@
+// The Computer Language Shootout
+// http://shootout.alioth.debian.org/
+// LRU Cache implementation in C++ by ndt0208
+
+#include <cstdint>
+#include <cstdlib>
+#include <iostream>
+#include <vector>
+
+struct LCG {
+    uint32_t seed;
+    explicit LCG(uint32_t s) : seed(s) {}
+
+    inline uint32_t next() {
+        constexpr uint32_t A = 1103515245u;
+        constexpr uint32_t C = 12345u;
+        constexpr uint32_t M = 1u << 31;
+        seed = (A * seed + C) % M;
+        return seed;
+    }
+};
+
+struct Node {
+    uint32_t key;
+    uint32_t val;
+    uint32_t prev;
+    uint32_t next;
+    uint32_t hnext;
+};
+
+class LRUCache {
+private:
+    uint32_t capacity;
+    uint32_t count;
+    uint32_t mask;
+    std::vector<uint32_t> buckets;
+    std::vector<Node> nodes;
+
+    inline uint32_t hash(uint32_t k) const {
+        return (k * 2654435761u) & mask;
+    }
+
+    inline void unlink_node(uint32_t idx) {
+        uint32_t p = nodes[idx].prev;
+        uint32_t n = nodes[idx].next;
+        nodes[p].next = n;
+        nodes[n].prev = p;
+    }
+
+    inline void insert_head(uint32_t idx) {
+        uint32_t head = nodes[0].next;
+        nodes[idx].prev = 0;
+        nodes[idx].next = head;
+        nodes[0].next = idx;
+        nodes[head].prev = idx;
+    }
+
+public:
+    explicit LRUCache(uint32_t cap) : capacity(cap), count(0) {
+        uint32_t bsize = 16;
+        while (bsize < cap * 2) {
+            bsize <<= 1;
+        }
+        mask = bsize - 1;
+        buckets.assign(bsize, 0);
+        nodes.resize(cap + 1);
+        nodes[0].prev = 0;
+        nodes[0].next = 0;
+    }
+
+    inline bool get(uint32_t key) {
+        uint32_t b = hash(key);
+        uint32_t idx = buckets[b];
+        while (idx != 0 && nodes[idx].key != key) {
+            idx = nodes[idx].hnext;
+        }
+        if (idx == 0) return false;
+
+        unlink_node(idx);
+        insert_head(idx);
+        return true;
+    }
+
+    inline void put(uint32_t key, uint32_t val) {
+        uint32_t b = hash(key);
+        uint32_t idx = buckets[b];
+        while (idx != 0 && nodes[idx].key != key) {
+            idx = nodes[idx].hnext;
+        }
+
+        if (idx != 0) {
+            nodes[idx].val = val;
+            unlink_node(idx);
+            insert_head(idx);
+            return;
+        }
+
+        if (count < capacity) {
+            count++;
+            idx = count;
+        } else {
+            idx = nodes[0].prev; // LRU tail
+            uint32_t old_b = hash(nodes[idx].key);
+            if (buckets[old_b] == idx) {
+                buckets[old_b] = nodes[idx].hnext;
+            } else {
+                uint32_t curr = buckets[old_b];
+                while (nodes[curr].hnext != idx) {
+                    curr = nodes[curr].hnext;
+                }
+                nodes[curr].hnext = nodes[idx].hnext;
+            }
+            unlink_node(idx);
+        }
+
+        nodes[idx].key = key;
+        nodes[idx].val = val;
+        nodes[idx].hnext = buckets[b];
+        buckets[b] = idx;
+        insert_head(idx);
+    }
+};
+
+int main(int argc, char **argv) {
+    uint32_t size = 100;
+    uint32_t n = 1000;
+    if (argc > 1) {
+        size = std::strtoul(argv[1], nullptr, 10);
+    }
+    if (argc > 2) {
+        n = std::strtoul(argv[2], nullptr, 10);
+    }
+
+    const uint32_t modular = size * 10;
+    LCG rng0(0);
+    LCG rng1(1);
+
+    LRUCache lru(size);
+    uint32_t hit = 0;
+    uint32_t missed = 0;
+
+    for (uint32_t i = 0; i < n; ++i) {
+        uint32_t n0 = rng0.next() % modular;
+        lru.put(n0, n0);
+        uint32_t n1 = rng1.next() % modular;
+        if (lru.get(n1)) {
+            hit++;
+        } else {
+            missed++;
+        }
+    }
+
+    std::cout << hit << '\n' << missed << '\n';
+    return 0;
+}
diff --git a/bench/bench_cpp.yaml b/bench/bench_cpp.yaml
index e17d7c0a5..342af82a7 100644
--- a/bench/bench_cpp.yaml
+++ b/bench/bench_cpp.yaml
@@ -18,6 +18,9 @@ problems:
   - name: nsieve
     source:
       - 1.cpp
+  - name: lru
+    source:
+      - 1.cpp
 compiler_version_command:
 compiler_version_regex:
 runtime_version_parameter: