Extra Characters in a String

CMakeLists.txt

@@ -148,6 +148,7 @@ add_task(evaluate-division)
 add_task(evaluate-reverse-polish-notation)
 add_task(excel-sheet-column-number)
 add_task(excel-sheet-column-title)
+add_task(extra-characters-in-a-string)
 add_task(factorial-trailing-zeroes)
 add_task(fair-distribution-of-cookies)
 add_task(fibonacci-number)

solutions/extra-characters-in-a-string/CMakeLists.txt

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

solutions/extra-characters-in-a-string/solution.hpp

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <algorithm>
+#include <string>
+#include <unordered_set>
+#include <vector>
+
+class Solution {
+public:
+  static int minExtraChar(std::string s,
+                          const std::vector<std::string> &dictionary) {
+    const int n = s.size();
+    const std::unordered_set<std::string> words{dictionary.begin(),
+                                                dictionary.end()};
+
+    std::vector<int> dp(n + 1);
+    for (int i = 1; i <= n; ++i) {
+      dp[i] = n;
+      for (int j = 0; j < i; ++j) {
+        const auto extra = words.count(s.substr(j, i - j)) ? 0 : i - j;
+        dp[i] = std::min(dp[i], dp[j] + extra);
+      }
+    }
+    return dp.back();
+  }
+};

solutions/extra-characters-in-a-string/test.cpp

@@ -0,0 +1,16 @@
+#include <catch.hpp>
+
+#include <solution.hpp>
+
+TEST_CASE("Simple") {
+  {
+    std::vector<std::string> dictionary{"leet", "code", "leetcode"};
+    std::string s = "leetscode";
+    REQUIRE(1 == Solution::minExtraChar(s, dictionary));
+  }
+  {
+    std::vector<std::string> dictionary{"hello", "world"};
+    std::string s = "sayhelloworld";
+    REQUIRE(3 == Solution::minExtraChar(s, dictionary));
+  }
+}