DP-Algo

Algorithm/Recursion/P1044 [NOIP 2003 普及组] 栈.cpp

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+#include <iostream>
+#include <set>
+#include <deque>
+using namespace std;
+set<deque<int>> result;
+void dfs(deque<int>& path, deque<int>& stack, deque<int>& left){
+	if(stack.size() == 0 && left.size() == 0){
+		result.emplace(path);
+		return;
+	}
+	else if(stack.size() == 0){
+		int tmp = left.front();
+		stack.push_back(tmp);
+		left.pop_front();
+		dfs(path, stack, left);
+		left.push_front(tmp);
+		stack.pop_back();
+	}
+	else if(left.size() == 0){
+		int tmp = stack.back();
+		stack.pop_back();
+		path.push_back(tmp);
+		dfs(path, stack, left);
+		stack.push_back(tmp);
+		path.pop_back();
+	} 
+	else {
+    {
+        int tmp = left.front();
+        left.pop_front();
+        stack.push_back(tmp);
+        dfs(path, stack, left);
+        stack.pop_back();
+        left.push_front(tmp);
+    }
+    {
+        int tmp = stack.back();
+        stack.pop_back();
+        path.push_back(tmp);
+        dfs(path, stack, left);
+        path.pop_back();
+        stack.push_back(tmp);
+    }
+}
+
+}
+
+int main(){
+	int n;
+	cin >> n;
+	deque<int> l(n), s, p;
+	for(int i = 0; i < n; i++){
+		l[i] = i + 1;
+	}
+	dfs(p, s, l);
+	cout << result.size() << endl;
+	/*
+	for(auto x : result){
+		for(auto y : x){
+			cout << y << " ";
+		}
+		cout << endl;
+	}*/
+	for(auto x : *result.begin()){
+		cout << x << " ";
+	}
+	cout << endl;
+	return 0;
+}