Leetcode 277 Find the Celebrity

最新推荐文章于 2020-05-25 03:09:59 发布

原创最新推荐文章于 2020-05-25 03:09:59 发布 · 134 阅读

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本文探讨了在一组人中快速识别出唯一名人的算法。首先通过一次遍历找到可能的名人候选，再进行二次验证确认其是否为真正的名人，整体时间复杂度为O(n)。文章详细解释了算法原理及其实现过程。

Problem:

在这里插入图片描述

Analysis:

method1:
first of all, we can use the array with 2 dimensions to check each pair, which time complexity will be O(n^2)

method2:

the first pass for all the people, find the celebrity candidate who doesn’t know anyone.

if (knows(A, B)):
* A is not Celebrity;
else:
* B is not Celebrity }

the second pass, to make sure that the candidate is indeed the celebrity, or return -1;

/**
 * 
 * @author shaohua
 *boolean knows(A, B)
 *
 * 1. find the celebrity candidate who doesn't know the person behind him
 * 2. make sure candidate is celebrity
 *
 */

public class Solution1 {
	public int findCelebrity(int n) {
		
		int candidate = 0;
		for (int i=1; i<n; i++) {
			if (knows(candidate, i)) {
				candidate = i;
			}
		}
		
		for(int i=0; i<n; i++) {
			if (candidate == i) {
				continue;
			}
			
			if (knows(candidate,i) || !knows(i,candidate)) {
				return -1;
			}
		}
		
		return candidate;	
	}	
}