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CodeForces/Codeforces Round 1007 (Div. 2)/B_Perfecto.cpp

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+#include <bits/stdc++.h>
+#define lo long long
+#define INF INT_MAX
+#define LLM LONG_LONG_MAX
+#define endl "\n"
+
+using namespace std;
+const int N = 1e7 + 10;
+/*
+    toothless. #17
+    @fredcss_dev
+*/
+
+bool f(lo x) {
+    if (x < 0) return false;
+    lo root = sqrtl(x);
+    return root * root == x;
+}
+
+void wczffl_503() {
+    int n;
+    cin >> n;
+    lo total = 1LL * n * (n + 1) / 2;
+    if (f(total)) {
+        cout << "-1\n";
+        return;
+    }
+    vector<lo> s(n + 1);
+    for (int i = 1; i <= n; ++i) {
+        s[i] = (2LL * n - i + 1) * i / 2;
+    }
+    vector<bool> jhd(n + 1, false);
+    for (int i = 1; i <= n - 1; ++i) {
+        if (f(s[i])) {
+            jhd[i] = true;
+        }
+    }
+    bool bad = false;
+    for (int i = 1; i <= n; ++i) {
+        lo now = s[i];
+        if (i <= n - 1 && jhd[i]) {
+            now--;
+        }
+        if (f(now)) {
+            bad = true;
+            break;
+        }
+    }
+    if (bad) {
+        cout << "-1\n";
+        return;
+    }
+    vector<int> p(n);
+    for (int i = 0; i < n; ++i) {
+        p[i] = n - i;
+    }
+    for (int i = 1; i <= n - 1; ++i) {
+        if (jhd[i]) {
+            swap(p[i - 1], p[i]);
+        }
+    }
+    for (int x : p) {
+        cout << x << ' ';
+    }
+    cout << '\n';
+}
+
+signed main()
+{
+    int t;
+    cin >> t;
+    while (t--) {
+        wczffl_503();
+    }
+    return 0;
+}