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-rw-r--r--other/num_squareful_arrays.cpp59
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diff --git a/other/num_squareful_arrays.cpp b/other/num_squareful_arrays.cpp
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--- a/other/num_squareful_arrays.cpp
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-// 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
-}