aboutsummaryrefslogtreecommitdiff
path: root/other/num_squareful_arrays.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'other/num_squareful_arrays.cpp')
-rw-r--r--other/num_squareful_arrays.cpp59
1 files changed, 59 insertions, 0 deletions
diff --git a/other/num_squareful_arrays.cpp b/other/num_squareful_arrays.cpp
new file mode 100644
index 0000000..a7fc481
--- /dev/null
+++ b/other/num_squareful_arrays.cpp
@@ -0,0 +1,59 @@
+// 996. Number of Squareful Arrays
+#include "leetcode.h"
+
+/*
+ * an array is squareful if the sum of every pair of adjacent elements is a
+ * perfect square. given an intger array nums, return the number of permutations
+ * of 'nums' that are squareful. two permutations 'perm1' and 'perm2' are
+ * different if there is some index 'i' such that 'perm1[i] != perm2[i]'.
+ */
+
+class Solution {
+ bool is_square(int x) {
+ int t = sqrt(x);
+ return t * t == x;
+ }
+ int fact(int x) {
+ int t = 1;
+ for (int i = 2; i <= x; i++)
+ t *= i;
+ return t;
+ }
+
+public:
+ int numSquarefulPerms(vector<int> &nums) {
+ int n = nums.size(), cnt = 1;
+ sort(nums.begin(), nums.end());
+ vector<int> s;
+ for (int i = 1; i < n; i++) {
+ if (nums[i] != nums[i - 1]) {
+ s.push_back(cnt);
+ cnt = 0;
+ }
+ cnt++;
+ }
+ s.push_back(cnt);
+ vvd f(1 << n, vector<int>(n, 0));
+ for (int i = 0; i < n; i++)
+ f[1 << i][i] = 1;
+ for (int S = 1; S < 1 << n; S++)
+ for (int i = 0; i < n; i++)
+ if (S & (1 << i))
+ for (int j = 0; j < n; j++)
+ if (!(S & (1 << j)) && is_square(nums[i] + nums[j]))
+ f[S | (1 << j)][j] += f[S][i];
+ int ans = 0;
+ for (int i = 0; i < n; i++)
+ ans += f[(1 << n) - 1][i];
+ for (int i = 0; i < s.size(); i++)
+ ans /= fact(s[i]);
+ return ans;
+ }
+};
+
+int main() {
+ Solution obj;
+ vector<int> n1 = {1, 17, 8}, n2 = {2, 2, 2};
+ printf("%d\n", obj.numSquarefulPerms(n1)); // expect: 2
+ printf("%d\n", obj.numSquarefulPerms(n2)); // expect: 1
+}