From dc409b79c15ac88e3911935e6114a9215e36ae07 Mon Sep 17 00:00:00 2001
From: Bulakh Igor <igorbulakh1987@yandex.ru>
Date: Sun, 8 Sep 2019 05:31:08 +0300
Subject: [PATCH] josephus permutation is done

---
 josephus_permutation/josephus_permutation.cpp | 102 +++++++++++-------
 josephus_permutation/solution.cpp             |  35 ++++++
 2 files changed, 100 insertions(+), 37 deletions(-)
 create mode 100644 josephus_permutation/solution.cpp

diff --git a/josephus_permutation/josephus_permutation.cpp b/josephus_permutation/josephus_permutation.cpp
index f940392..fbea1a3 100644
--- a/josephus_permutation/josephus_permutation.cpp
+++ b/josephus_permutation/josephus_permutation.cpp
@@ -15,46 +15,46 @@ using namespace std;
 
 template<typename RandomIt>
 void MakeJosephusPermutation(RandomIt first, RandomIt last, uint32_t step_size) {
-//    deque<typename RandomIt::value_type> pool(make_move_iterator(first), make_move_iterator(last));
-//
-//    size_t cur_pos = 0;
-//    while (!pool.empty()) {
-//        *(first++) = move(pool[cur_pos]);
-//        pool.erase(pool.begin() + cur_pos);
-//        if (pool.empty()) {
-//            break;
-//        }
-////        cout << cur_pos << " " << step_size << " " << pool.size() << " " << (last - first) << endl;
-//        cur_pos = (cur_pos + step_size - 1) % pool.size();
-//    }
+/*    deque<typename RandomIt::value_type> pool(make_move_iterator(first), make_move_iterator(last));
 
-//    list<typename RandomIt::value_type> pool(make_move_iterator(first), make_move_iterator(last));
-//    list<typename RandomIt::value_type> pool;
-//    move(first,last,back_inserter(pool));
-//
-//    auto it = pool.begin();
-//
-//    while (!pool.empty()) {
-//
-//        *(first++) = move(*it);
-//        it = pool.erase(it);
-//        if (pool.empty()) {
-//            break;
-//        }
-//
-//        size_t dist = distance(it, pool.end());
-//
-//        if (dist <= step_size - 1) {
-//            it = pool.begin();
-//            if (next(it) != pool.end()) {
-//                it = next(it, step_size - dist - 1);
-//            }
-//        } else {
-//            it = next(it, step_size - 1);
-//        }
-//    }
+    size_t cur_pos = 0;
+    while (!pool.empty()) {
+        *(first++) = move(pool[cur_pos]);
+        pool.erase(pool.begin() + cur_pos);
+        if (pool.empty()) {
+            break;
+        }
+//        cout << cur_pos << " " << step_size << " " << pool.size() << " " << (last - first) << endl;
+        cur_pos = (cur_pos + step_size - 1) % pool.size();
+    }
 
+    list<typename RandomIt::value_type> pool(make_move_iterator(first), make_move_iterator(last));
     list<typename RandomIt::value_type> pool;
+    move(first,last,back_inserter(pool));
+
+    auto it = pool.begin();
+
+    while (!pool.empty()) {
+
+        *(first++) = move(*it);
+        it = pool.erase(it);
+        if (pool.empty()) {
+            break;
+        }
+
+        size_t dist = distance(it, pool.end());
+
+        if (dist <= step_size - 1) {
+            it = pool.begin();
+            if (next(it) != pool.end()) {
+                it = next(it, step_size - dist - 1);
+            }
+        } else {
+            it = next(it, step_size - 1);
+        }
+    }*/
+
+    /*list<typename RandomIt::value_type> pool;
     move(first, last, back_inserter(pool));
     size_t cur_pos = 0;
     size_t pred_pos = 0;
@@ -75,8 +75,36 @@ void MakeJosephusPermutation(RandomIt first, RandomIt last, uint32_t step_size)
 
         pred_pos = cur_pos;
         cur_pos = (cur_pos + step_size - 1) % pool.size();
+    }*/
+
+    const uint32_t range_size = last - first;
+    if (range_size <= 2) {
+        return;
     }
 
+    vector<uint32_t> next_alive_positions(range_size);
+    iota(begin(next_alive_positions), end(next_alive_positions), 1);
+    next_alive_positions.back() = 0;
+
+    vector<typename RandomIt::value_type> permutation;
+    uint32_t current_position = 0;
+    uint32_t prev_alive_position = range_size - 1;
+
+    for (uint32_t step_index = 0; step_index < range_size; ++step_index) {
+        permutation.push_back(move(*(first + current_position)));
+        next_alive_positions[prev_alive_position] = next_alive_positions[current_position];
+        for (uint32_t i = 0; i < step_size; ++i) {
+            if (i > 0) {
+                prev_alive_position = current_position;
+            }
+            current_position = next_alive_positions[current_position];
+        }
+    }
+//    for (uint32_t i = 0; i < range_size; ++i, ++first) {
+//        *first = move(permutation[i]);
+//    }
+
+    move(begin(permutation), end(permutation), first);
 }
 
 vector<int> MakeTestVector() {
diff --git a/josephus_permutation/solution.cpp b/josephus_permutation/solution.cpp
new file mode 100644
index 0000000..bc65802
--- /dev/null
+++ b/josephus_permutation/solution.cpp
@@ -0,0 +1,35 @@
+#include <list>
+#include <cstdint>
+#include <iterator>
+#include <utility>
+
+using namespace std;
+
+
+// Вспомогательная функция, позволяющая «зациклить» список
+template <typename Container, typename ForwardIt>
+ForwardIt LoopIterator(Container& container, ForwardIt pos) {
+    return pos == container.end() ? container.begin() : pos;
+}
+
+template <typename RandomIt>
+void MakeJosephusPermutation(RandomIt first, RandomIt last,
+                             uint32_t step_size) {
+    list<typename RandomIt::value_type> pool;
+    for (auto it = first; it != last; ++it) {
+        pool.push_back(move(*it));
+    }
+    auto cur_pos = pool.begin();
+    while (!pool.empty()) {
+        *(first++) = move(*cur_pos);
+        if (pool.size() == 1) {
+            break;
+        }
+        const auto next_pos = LoopIterator(pool, next(cur_pos));
+        pool.erase(cur_pos);
+        cur_pos = next_pos;
+        for (uint32_t step_index = 1; step_index < step_size; ++step_index) {
+            cur_pos = LoopIterator(pool, next(cur_pos));
+        }
+    }
+}