// 765. Couples Holding Hands #include #include /* * 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. */ int minSwapsCouples(int *row, int row_size) { int pair[60], position[60], cnt = 0; for (int i = 0; i < 60; i += 2) { pair[i] = i + 1; pair[i + 1] = i; } for (int i = 0; i < row_size; i++) position[row[i]] = i; for (int i = 0; i < row_size; i += 2) { if (row[i + 1] != pair[row[i]]) { cnt++; int pos = position[pair[row[i]]]; position[row[i + 1]] = pos; int tmp = row[pos]; row[pos] = row[i + 1]; row[i + 1] = tmp; position[pair[row[i]]] = i + 1; } } return cnt; } int main() { int r1[] = {0, 2, 1, 3}, r2[] = {3, 2, 0, 1}; printf("%d\n", minSwapsCouples(r1, 4)); // expect: 1 printf("%d\n", minSwapsCouples(r2, 4)); // expect: 0 }