Create APIO 22-perm.cpp

Author: dolphingarlic

APIO/APIO 22-perm.cpp

@@ -0,0 +1,56 @@
+#include "perm.h"
+ 
+#include <bits/stdc++.h>
+using namespace std;
+ 
+vector<int> construct_permutation(long long k) {
+    int bit = 64 - __builtin_clzll(k);
+    vector<double> ans;
+    bool flag = false;
+    while (bit > 0) {
+        bit -= 2;
+        if (bit == -1) {
+            ans.push_back(1e9);
+            if (k & 1) ans.push_back(-1e9);
+        } else {
+            int val = (k >> bit) & 3;
+            if (ans.empty()) {
+                if (val == 2) ans = {0};
+                else ans = {1, 0}, flag = true;
+            } else {
+                if (val == 0) {
+                    ans.push_back(1e9);
+                    ans.push_back(1e9 + 1);
+                } else if (val == 1) {
+                    ans.push_back(1e9);
+                    ans.push_back(1e9 + 1);
+                    ans.push_back(-1e9);
+                    flag = true;
+                } else if (val == 2) {
+                    ans.push_back(1e9);
+                    ans.push_back(-1e9);
+                    ans.push_back(1e9 + 1);
+                    flag = true;
+                } else {
+                    if (!flag) {
+                        ans.push_back(1e9);
+                        ans.push_back(-1e9);
+                        ans.push_back(1e9 + 1);
+                        ans.push_back(-1e9 - 1);
+                        flag = true;
+                    } else {
+                        ans.push_back(1e9);
+                        ans.push_back(1e9 + 1);
+                        ans.push_back(1.5);
+                    }
+                }
+            }
+        }
+        vector<double> uni(ans.begin(), ans.end());
+        sort(uni.begin(), uni.end());
+        for (auto &it : ans)
+            it = lower_bound(uni.begin(), uni.end(), it) - uni.begin();
+    }
+ 
+    return vector<int>(ans.begin(), ans.end());
+}