CELEBRITY

/* The knows API is defined for you.
      bool knows(int a, int b); */
//1,2,3
class Solution {
public:
    int findCelebrity(int n) {
       int cand = 0;
        for (int i = 0; i < n; ++i) {
            if(knows(cand,i)) {
                cand = i;
            }
        }
        int ans = 0;
        for(int i = 0; i < n; ++i) {
            if(knows(i,cand) and !knows(cand,i)) {
                ans++;
            }
        }

        return ans == n - 1 ? cand : -1;
    }
};