【leetcode78】Single Number II
2016-07-31 15:29
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题目描述:
给定一个数组,里面除了一个数字,其他的都出现三次。求出这个数字
原文描述:
Given an array of integers, every element appears three times except for one. Find that single one.Note:
Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?Subscribe to see which companies asked this question
思路:
设置一个32位的数组,然然后对数组,Array【i】代表i位的1个数,统计整个数组nums【】的数字,对于每个Array【i】做mod3的运算遍历nums【】数组时候,是左移&1取出,加到Array【i】上面,然后mod3
最后右移加到result上面
代码:
// Single Number II // 方法1,时间复杂度O(n),空间复杂度O(1) public class Solution { public int singleNumber(int[] nums) { final int W = Integer.SIZE; // 一个整数的bit数,即整数字长 int[] count = new int[W]; // count[i]表示在在i位出现的1的次数 for (int i = 0; i < nums.length; i++) { for (int j = 0; j < W; j++) { count[j] += (nums[i] >>> j) & 1; count[j] %= 3; } } int result = 0; for (int i = 0; i < W; i++) { result += (count[i] << i); } return result; } };
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