Description

Given an integer sequence, say {6, 1, 3, 4, 5, 2}, can we sort the sequence by keeping swapping the first number with its two neighbors: the second number and the last number ? 

For example, Swap the first number 6 and with the last number 2 to get {2, 1, 3, 4, 5, 6}, and then swap the first number 2 and the second number 1 to get {1, 2, 3, 4, 5, 6}, and we get the sequence sorted.

In function.h we define a class called SwapSort. A constructor and a member function show_solutions are implemented. Your task is to complete the implementation of the following two functions:

1. set<State> extend(State s);
A State is defined as using State = vector<int>;
For some State s, we may extend it by swapping the first number with the second one, or swapping the first number with the last one. Therefore, from State s we may generate two new states, and insert them into a set.

2. void solve(int steps);
This function tries to solve the problem in a number of swaps specified by steps. The found solutions are stored in the class member set<list<State>> _solutions;

Notice that, no duplicate states are allowed in a solution.

You need to implement the two functions in function.cpp

main.cpp

#include "function.h" int main() { State s;// = {2, 1, 3}; int e; while (cin >> e) { // press Ctrl + Z to end the input s.push_back(e); } SwapSort prob1(s); prob1.solve(4); prob1.show_solutions(); cout << "\n"; }

function.h

#ifndef _SWAPSORT_ #define _SWAPSORT_ #include <iostream> #include <vector> #include <set> #include <list> #include <algorithm> using namespace std; using State = vector<int>; class SwapSort { private: set<list<State>> _paths; set<list<State>> _solutions; set<State> _explored; public: SwapSort(State init) { list<State> ls; ls.push_back(init); _paths.insert(ls); } void show_solutions() { if (_solutions.size()==0) { cout << "No solution.\n"; } else { for (auto p : _solutions) { for (auto s : p) { for (auto i : s) { cout << i << " "; } cout << "-> "; } cout << ".\n"; } } } set<State> extend(State s); void solve(int steps); }; #endif

function.cpp

#include "function.h" set<State> SwapSort::extend(State s) { set<State> SS; // your code here return SS; } void SwapSort::solve(int steps) { while (steps>0) { set<list<State>> oldPaths; set<list<State>> newPaths; for (auto p : _paths) { // your code here } for (auto p : oldPaths) { _paths.erase(p); } for (auto p : newPaths) { _paths.insert(p); } --steps; } }

Input

An integer sequence, separated by spaces. End by EOF.

Output

The output will be generated by function.h

Sample Input  Download

Sample Output  Download

Partial Judge Code

12329.cpp

Partial Judge Header

12329.h

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