Pass the Pillow

summary

• The problem is to find the index of the person holding the pillow after a given time in a line of people passing the pillow in both directions.

approach

• The approach is to calculate the number of complete rounds the pillow makes and the remaining time, then determine the person holding the pillow based on the time.

complexity

• O(1)

explain

• The code first calculates the number of complete rounds the pillow makes by dividing the time by the number of people minus one
• If the time is odd, the remaining time is the person holding the pillow, otherwise, it is the person after the remaining time
• The code returns the index of the person holding the pillow.

Solution Code:

class Solution {
public:
    int passThePillow(int n, int time) {
        int a = time / (n-1);
        if(a&1){
            return n - time % (n-1);
        } else{
            return 1 + time % (n-1);
        }
    }
};