[10_recursive] one_two_step, nonrecursive version, done.

ycl113 · Oct 12, 2018 · 5a374e0 · 5a374e0
1 parent 07297f8
commit 5a374e0
Showing 1 changed file with 48 additions and 4 deletions.
diff --git a/c-cpp/10_recursive/one_two_step.cc b/c-cpp/10_recursive/one_two_step.cc
@@ -6,7 +6,13 @@ class SolutionOFOneTwoStep {
     static std::unordered_map<size_t, size_t> result_;
 
   public:
-    size_t operator()(size_t steps) {
+    enum class POLICY {
+        RECURSIVE,
+        NONRECURSIVE
+    };
+
+  private:
+    size_t recursive(size_t steps) {
         auto iter = result_.find(steps);
         if (result_.end() != iter) {  // found.
             return iter->second;
@@ -16,12 +22,50 @@ class SolutionOFOneTwoStep {
             return res;
         }
     }
+    size_t nonrecursive(size_t steps) {
+        auto iter = result_.find(steps);
+        if (result_.end() != iter) {  // found.
+            return iter->second;
+        } else {
+            size_t start;
+            for (start = steps; start != 2 and result_.end() == result_.find(start); --start) {}
+            for (size_t i = start; i != steps; ++i) {
+                result_.insert({i + 1, result_[i - 1] + result_[i]});
+            }
+            return result_[steps];
+        }
+    }
+
+  public:
+    size_t operator()(size_t steps, const POLICY policy = POLICY::RECURSIVE) {
+        if (policy == POLICY::RECURSIVE) {
+            return recursive(steps);
+        } else if (policy == POLICY::NONRECURSIVE) {
+            return nonrecursive(steps);
+        }
+    }
+    static void debug() {
+        for (auto kv : result_) {
+            std::cout << kv.first << ' ' << kv.second << std::endl;
+        }
+        std::cout << std::endl;
+    }
 };
 
-std::unordered_map<size_t, size_t>
-    SolutionOFOneTwoStep::result_ = {{1, 1}, {2, 2}};
+std::unordered_map<size_t, size_t> SolutionOFOneTwoStep::result_ = {{1, 1}, {2, 2}};
 
 int main() {
-    std::cout << SolutionOFOneTwoStep()(10) << std::endl;
+    SolutionOFOneTwoStep::debug();
+
+    std::cout << SolutionOFOneTwoStep()(5, SolutionOFOneTwoStep::POLICY::RECURSIVE) << std::endl;
+    SolutionOFOneTwoStep::debug();
+
+    std::cout << SolutionOFOneTwoStep()(10, SolutionOFOneTwoStep::POLICY::NONRECURSIVE) << std::endl;
+    SolutionOFOneTwoStep::debug();
+
+    std::cout << SolutionOFOneTwoStep()(20, SolutionOFOneTwoStep::POLICY::RECURSIVE) << std::endl;
+    SolutionOFOneTwoStep::debug();
+
     return 0;
 }
+