cpp: add «2149. Rearrange Array Elements by Sign»

Signed-off-by: Matej Focko <mfocko@redhat.com>

cpp/rearrange-array-elements-by-sign.cpp

@@ -0,0 +1,86 @@
+#include <cassert>
+#include <vector>
+
+class Solution {
+    template <typename C> struct arr_iterator {
+        using It = typename C::const_iterator;
+
+        It it, end;
+
+        arr_iterator(const C &container)
+            : it(container.begin()), end(container.end()) {}
+
+        void init() {
+            while (it != end && !predicate(*it)) {
+                ++it;
+            }
+        }
+
+        auto operator!=(const It &other_it) const -> bool {
+            return it != other_it;
+        }
+
+        auto operator*() const -> int { return *it; }
+
+        void operator++() {
+            do {
+                ++it;
+            } while (it != end && !predicate(*it));
+        }
+
+        virtual auto predicate(int x) const -> bool = 0;
+        virtual ~arr_iterator() {}
+    };
+
+    template <typename C> struct pos_iterator : arr_iterator<C> {
+        pos_iterator(const C &container) : arr_iterator<C>(container) {
+            arr_iterator<C>::init();
+        }
+        auto predicate(int x) const -> bool override { return x > 0; }
+    };
+
+    template <typename C> struct neg_iterator : arr_iterator<C> {
+        neg_iterator(const C &container) : arr_iterator<C>(container) {
+            arr_iterator<C>::init();
+        }
+        auto predicate(int x) const -> bool override { return x < 0; }
+    };
+
+  public:
+    std::vector<int> rearrangeArray(const std::vector<int> &nums) {
+        std::vector<int> result;
+
+        auto positive = pos_iterator(nums);
+        auto negative = neg_iterator(nums);
+
+        for (bool finished = false; !finished;) {
+            finished = true;
+
+            if (positive != nums.end()) {
+                result.push_back(*positive);
+
+                ++positive;
+                finished = false;
+            }
+
+            if (negative != nums.end()) {
+                result.push_back(*negative);
+
+                ++negative;
+                finished = false;
+            }
+        }
+
+        return result;
+    }
+};
+
+int main() {
+    Solution s;
+
+    assert((s.rearrangeArray(std::vector{3, 1, -2, -5, 2, -4}) ==
+            std::vector{3, -2, 1, -5, 2, -4}));
+    assert((s.rearrangeArray(std::vector{-1, 1}) == std::vector{1, -1}));
+
+    return 0;
+}