132 Pattern

CMakeLists.txt

@@ -23,6 +23,7 @@ endfunction()
 enable_testing()
 
 add_task(01-matrix)
+add_task(132-pattern)
 add_task(3sum)
 add_task(3sum-closest)
 add_task(add-binary)

solutions/132-pattern/CMakeLists.txt

@@ -0,0 +1 @@
+add_catch(test_132_pattern test.cpp)

solutions/132-pattern/solution.hpp

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <climits>
+#include <stack>
+#include <vector>
+
+class Solution {
+public:
+  static bool find132pattern(const std::vector<int> &nums) {
+    int middle = INT_MIN;
+    std::stack<int> stack;
+
+    for (int i = nums.size() - 1; i >= 0; --i) {
+      if (nums[i] < middle) {
+        return true;
+      }
+
+      while (!stack.empty() && stack.top() < nums[i]) {
+        middle = stack.top();
+        stack.pop();
+      }
+
+      stack.push(nums[i]);
+    }
+
+    return false;
+  }
+};

solutions/132-pattern/test.cpp

@@ -0,0 +1,22 @@
+#include <catch.hpp>
+
+#include <solution.hpp>
+
+TEST_CASE("Simple") {
+  {
+    std::vector<int> nums{1, 2, 3, 4};
+    REQUIRE_FALSE(Solution::find132pattern(nums));
+  }
+  {
+    std::vector<int> nums{3, 1, 4, 2};
+    REQUIRE(Solution::find132pattern(nums));
+  }
+  {
+    std::vector<int> nums{-1, 3, 2, 0};
+    REQUIRE(Solution::find132pattern(nums));
+  }
+  {
+    std::vector<int> nums{1, 0, 1, -4, -3};
+    REQUIRE_FALSE(Solution::find132pattern(nums));
+  }
+}