add cmake/tests and onboard a edit distance solution with compressed …

…memory usage

.gitignore

@@ -0,0 +1,2 @@
+build
+.idea

CMakeLists.txt

@@ -0,0 +1,10 @@
+cmake_minimum_required(VERSION 3.10)
+
+project(LeetCode VERSION 1.0)
+
+set (CMAKE_CXX_STANDARD 11)
+
+include_directories(PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
+
+enable_testing()
+add_subdirectory(tests)

Dynamic_Programming/072.Edit-Distance/072.Edit-Distance.cpp

@@ -30,4 +30,53 @@ class Solution {
 
         return dp[n1][n2];
     }
+
+    /**
+     * @brief calculate the minimum edit distance between word1 and word2
+     * Another implementation of edit distance with compressed memory usage
+     * @param word1 const std::string &   The reference of first string
+     * @param word2 const std::string &   The reference of second string
+     * @return The edit distance
+     */
+    int minDistance2(const std::string &word1, const std::string &word2)
+    {
+      int n1=word1.size();
+      int n2=word2.size();
+
+      // dp[i][j] : edit distance between word1[0, i) and word2[0, j)
+      // dp[i][j] = std::min(dp[i-1][j], dp[i][j-1], dp[i-1][j-1]) + 1
+      //                     ----------  ---------- -------------
+      //                       add-j       delete-j   replace-j
+      //  if word1[i] != word2[j]
+      // Compressed to
+      // dp[j]
+
+      std::vector<int> dp(n2+1, 0);
+
+      for (auto j = 1; j <= n2; ++j)
+        dp[j] = j; // distance between word1[0, 0) and word2[0, j), j deletions
+
+      for (auto i = 1; i <= n1; ++i)
+      {
+        int topleft = dp[0];
+        // reset dp[i]
+        dp[0] = i; // edit distance = j add operations
+
+        for (auto j = 1; j <= n2; ++j)
+        {
+          int top = dp[j];
+
+          if (word1[i-1] == word2[j-1])
+            dp[j] = topleft;
+          else
+            dp[j] = std::min({dp[j-1], top, topleft}) + 1;
+            //                -------- --- ---------
+            //                delete-j add-j replace-j
+
+          topleft = top; // move the top 1 step to the right
+        }
+      }
+
+      return dp.back();
+    }
 };

Readme.md

@@ -1195,4 +1195,4 @@
 [Bit_Manipulation](https://github.com/wisdompeak/LeetCode/tree/master/Template/Bit_manipulation)  
 [Combination-Number](https://github.com/wisdompeak/LeetCode/tree/master/Template/Combination-Number)  
 [RB_Tree](https://github.com/wisdompeak/LeetCode/tree/master/Template/RB_Tree)  
-[CPP_LANG](https://github.com/wisdompeak/LeetCode/tree/master/Template/CPP_LANG)    
+[CPP_LANG](https://github.com/wisdompeak/LeetCode/tree/master/Template/CPP_LANG)

tests/CMakeLists.txt

@@ -0,0 +1,12 @@
+include(FetchContent)
+
+FetchContent_Declare(
+  googletest
+  URL https://github.com/google/googletest/archive/609281088cfefc76f9d0ce82e1ff6c30cc3591e5.zip
+)
+
+FetchContent_MakeAvailable(googletest)
+
+include(GoogleTest)
+
+add_subdirectory(Dynamic_Programming)

tests/Dynamic_Programming/072.Edit-Distance/072.Edit-Distance.t.cpp

@@ -0,0 +1,17 @@
+#include "gtest/gtest.h"
+#include <climits>   // INT_MAX
+#include <algorithm> // std::min({})
+#include <vector>
+#include <string>
+using namespace std;
+
+#include <Dynamic_Programming/072.Edit-Distance/072.Edit-Distance.cpp>
+
+TEST(edit_distance_72_test, I)
+{
+  std::string word1 = "horse";
+  std::string word2 = "ros";
+
+  ASSERT_EQ(Solution().minDistance2(word1, word2), 3);
+  ASSERT_EQ(Solution().minDistance(word1, word2), 3);
+}

tests/Dynamic_Programming/072.Edit-Distance/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(BINARY edit_distance_test)
+
+add_executable(${BINARY} 072.Edit-Distance.t.cpp)
+
+target_link_libraries(${BINARY} gtest_main)
+
+include(GoogleTest)
+
+gtest_discover_tests(${BINARY})

tests/Dynamic_Programming/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory(072\.Edit-Distance)