Create solution.java

Author: samarthswami1016

solution/3400-3499/3470.Permutations IV/solution.java

@@ -0,0 +1,157 @@
+import java.util.*;
+
+class DPHelper {
+    static final long ok = 10000000000000000L;
+    long[][][] dp = new long[101][101][2];
+    boolean[][][] vis = new boolean[101][101][2];
+
+    long compute(int o, int e, int p) {
+        if (o == 0 && e == 0) return 1;
+        if (vis[o][e][p]) return dp[o][e][p];
+
+        long r = 0;
+        if (p == 1) {
+            if (o == 0) r = 0;
+            else r = o * compute(o - 1, e, 0);
+        } else {
+            if (e == 0) r = 0;
+            else r = e * compute(o, e - 1, 1);
+        }
+
+        if (r > ok) r = ok;
+        vis[o][e][p] = true;
+        dp[o][e][p] = r;
+        return r;
+    }
+}
+
+class SortHelper {
+    void sortList(ArrayList<Integer> list) {
+        Collections.sort(list);
+    }
+}
+
+class PermutationHelper {
+    List<Integer> buildPermutation(int p, ArrayList<Integer> O, ArrayList<Integer> E, long k, DPHelper d) {
+        List<Integer> ans = new ArrayList<>();
+        if (O.size() + E.size() == 0) return ans;
+        int i = 0;
+
+        if (p == 1) {
+            while (i < O.size()) {
+                long cnt = d.compute(O.size() - 1, E.size(), 0);
+                if (k > cnt) {
+                    k -= cnt;
+                    i++;
+                } else {
+                    int x = O.get(i);
+                    O.remove(i);
+                    ans.add(x);
+                    ans.addAll(buildPermutation(0, O, E, k, d));
+                    return ans;
+                }
+            }
+        } else {
+            while (i < E.size()) {
+                long cnt = d.compute(O.size(), E.size() - 1, 1);
+                if (k > cnt) {
+                    k -= cnt;
+                    i++;
+                } else {
+                    int x = E.get(i);
+                    E.remove(i);
+                    ans.add(x);
+                    ans.addAll(buildPermutation(1, O, E, k, d));
+                    return ans;
+                }
+            }
+        }
+        return ans;
+    }
+
+    List<Integer> alternateFormation(ArrayList<Integer> O, ArrayList<Integer> E, long k, DPHelper d, int n, SortHelper s) {
+        List<Integer> ans = new ArrayList<>();
+        int tot = O.size() + E.size();
+        if (tot % 2 == 1) {
+            int i = 0;
+            while (i < O.size()) {
+                long cnt = d.compute(O.size() - 1, E.size(), 0);
+                if (k > cnt) {
+                    k -= cnt;
+                } else {
+                    int x = O.get(i);
+                    O.remove(i);
+                    ans.add(x);
+                    ans.addAll(buildPermutation(0, O, E, k, d));
+                    return ans;
+                }
+                i++;
+            }
+        } else {
+            ArrayList<Integer> U = new ArrayList<>();
+            U.addAll(O);
+            U.addAll(E);
+            s.sortList(U);
+            int i = 0;
+            while (i < U.size()) {
+                int x = U.get(i);
+                if (O.contains(x)) {
+                    long cnt = d.compute(O.size() - 1, E.size(), 0);
+                    if (k > cnt) {
+                        k -= cnt;
+                    } else {
+                        int idx = O.indexOf(x);
+                        O.remove(idx);
+                        ans.add(x);
+                        ans.addAll(buildPermutation(0, O, E, k, d));
+                        return ans;
+                    }
+                } else {
+                    long cnt = d.compute(O.size(), E.size() - 1, 1);
+                    if (k > cnt) {
+                        k -= cnt;
+                    } else {
+                        int idx = E.indexOf(x);
+                        E.remove(idx);
+                        ans.add(x);
+                        ans.addAll(buildPermutation(1, O, E, k, d));
+                        return ans;
+                    }
+                }
+                i++;
+            }
+        }
+        return ans;
+    }
+}
+
+class Solution {
+    public int[] permute(int n, long k) {
+        int o = (n + 1) / 2, e = n / 2;
+        ArrayList<Integer> O = new ArrayList<>(), E = new ArrayList<>();
+
+        for (int i = 1; i <= n; i++) {
+            if (i % 2 == 1) O.add(i);
+            else E.add(i);
+        }
+
+        SortHelper s = new SortHelper();
+        s.sortList(O);
+        s.sortList(E);
+
+        DPHelper d = new DPHelper();
+        PermutationHelper ph = new PermutationHelper();
+
+        long tot = 0;
+        if (n % 2 == 1) tot = d.compute(O.size() - 1, E.size(), 0) * O.size();
+        else tot = d.compute(O.size() - 1, E.size(), 0) * O.size() + d.compute(O.size(), E.size() - 1, 1) * E.size();
+
+        if (k > tot) return new int[0];
+
+        List<Integer> res = ph.alternateFormation(O, E, k, d, n, s);
+        int[] ans = new int[res.size()];
+        for (int i = 0; i < res.size(); i++) ans[i] = res.get(i);
+
+        return ans;
+    }
+}