Max product subarray (#189)

* add max product subarray * impl max product subarray
SKTT1Ryze · Mar 6, 2024 · a593b22 · a593b22
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diff --git a/leetcode-cc/MaxProductSubarray.hpp b/leetcode-cc/MaxProductSubarray.hpp
@@ -0,0 +1,71 @@
+#include <algorithm>
+
+#include "TestHelper.h"
+#include "problem.h"
+#include "solution.h"
+
+using namespace std;
+
+IMPLEMENT_PROBLEM_CLASS(PMaxProductSubarray, 152, DIFFI_MEDIUM,
+                        TOPIC_ALGORITHMS, "Maximum Product Subarray",
+                        "Given an integer array nums, find a subarray that has "
+                        "the largest product, and return the product.",
+                        {"DP"});
+
+class SMaxProductSubarray : public ISolution {
+ public:
+  size_t problemId() const override { return 152; }
+  string name() const override {
+    return ("Solution for " + string("Maximum Product Subarray"));
+  }
+  string location() const override { return __FILE_NAME__; }
+  int test() const override {
+    return testHelper<vector<int>, int>({{2, 3, -2, 4}, {-2, 0, -1}}, {6, 0},
+                                        [this](auto input) {
+                                          // return this->maxProduct(input);
+                                          return this->maxProductV2(input);
+                                        });
+  };
+  int benchmark() const override { return 0; }
+
+ private:
+  // work, but time limit
+  int maxProduct(vector<int>& nums) const {
+    int n = nums.size();
+    vector<vector<int>> dp(n, vector(n, 0));
+    int res = INT_MIN;
+
+    for (int i = 0; i < n; i++) {
+      dp[i][i] = nums[i];
+      res = max(res, dp[i][i]);
+    }
+
+    for (int i = 0; i < n; i++) {
+      for (int j = i + 1; j < n; j++) {
+        dp[i][j] = dp[i][j - 1] * nums[j];
+        res = max(res, dp[i][j]);
+      }
+    }
+
+    return res;
+  }
+
+  int maxProductV2(vector<int>& nums) const {
+    int n = nums.size();
+    if (n == 0) return 0;
+
+    int max_product = nums[0];
+    int min_product = nums[0];
+    int result = nums[0];
+
+    for (int i = 1; i < n; ++i) {
+      int temp_max = max_product;
+      int temp_min = min_product;
+      max_product = max({nums[i], nums[i] * temp_max, nums[i] * temp_min});
+      min_product = min({nums[i], nums[i] * temp_max, nums[i] * temp_min});
+      result = max(result, max_product);
+    }
+
+    return result;
+  }
+};
diff --git a/runtime-cc/src/registration.cc b/runtime-cc/src/registration.cc
@@ -44,6 +44,7 @@
 #include "../leetcode-cc/MaxDiffBetNodeAndAncestor.hpp"
 #include "../leetcode-cc/MaxLenOfConcatenatedStrWithUniqueChars.hpp"
 #include "../leetcode-cc/MaxPoints.hpp"
+#include "../leetcode-cc/MaxProductSubarray.hpp"
 #include "../leetcode-cc/MaximalRectangle.hpp"
 #include "../leetcode-cc/MergeKSortedLists.hpp"
 #include "../leetcode-cc/MergeSortedArray.hpp"
@@ -659,5 +660,10 @@ const int registerAll(std::shared_ptr<Container> handle) {
   handle->registerSolution(
       []() -> ArcSolution { return std::make_shared<SReverseWords>(); });
 
+  handle->registerProblem(
+      []() -> ArcProblem { return std::make_shared<PMaxProductSubarray>(); });
+  handle->registerSolution(
+      []() -> ArcSolution { return std::make_shared<SMaxProductSubarray>(); });
+
   return 0;
 }