// 765. Couples Holding Hands #include "leetcode.h" /* * there are 'n' couples sitting '2n' seats arranged in a row and want to hold * hands. the people and seats are represented by an integer array 'row' where * 'row[i]' is the id of the person sitting in the i'th seat. the couples are * numbered in order, the first couple being '(0, 1)', the second couple being * '(2, 3)', and so on with the last couple being '(2n -2, 2n -1)'. return the * minimum number of swaps so that every couple is sitting side by side. a swap * consists of choosing any two people then they stand up and switch seats. */ class Solution { public: int minSwapsCouples(vector &row) { int ans = 0, n = row.size(); vector ptn(n, 0), pos(n, 0); for (int i = 0; i < n; i++) { ptn[i] = (!(i % 2) ? i + 1 : i - 1); pos[row[i]] = i; } for (int i = 0; i < n; i++) for (int j = ptn[pos[ptn[row[i]]]]; i != j; j = ptn[pos[ptn[row[i]]]]) { swap(row[i], row[j]); swap(pos[row[i]], pos[row[j]]); ans++; } return ans; } }; int main() { Solution obj; vector r1 = {0, 2, 1, 3}, r2 = {3, 2, 0, 1}; printf("%d\n", obj.minSwapsCouples(r1)); // expect: 1 printf("%d\n", obj.minSwapsCouples(r2)); // expect: 0 }