Bit Manipulation

最新推荐文章于 2024-09-09 08:49:50 发布

bsbcarter

最新推荐文章于 2024-09-09 08:49:50 发布

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分类专栏： leetcode bit manipulation

本文链接：https://blog.youkuaiyun.com/bsbcarter/article/details/48674035

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本文探讨了位运算中的算术右移和逻辑右移的区别，并通过一个具体的例子展示了如何利用位运算来找出数组中唯一出现一次的数。文章还提供了一段Java代码实现，该实现使用位操作高效地解决了问题。

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1. >> 和 >>>

>> is arithmetic shift right, >>> is logical shift right.

In an arithmetic shift, the sign bit is extended to preserve the signedness of the number.

For example: -2 represented in 8 bits would be 11111110 (because the most significant bit has negative weight). Shifting it right one bit using arithmetic shift would give you 11111111, or -1. Logical right shift, however, does not care that the value could possibly represent a number; it simply moves everything to the right and fills in from the left with 0s. Shifting our -2 right one bit using logical shift would give 01111111.

public class Solution {
    public int singleNumber(int[] nums) {
        int [] counts = new int [32];
        for ( int i = 0; i < 32; i ++ ){
            for ( int j = 0; j < nums.length; j ++ ){
                counts[i] += (nums[j] >> i) & 1;
            }
        }
        int res = 0;
        for ( int i = 31; i >= 0; i -- ){
            res += counts[i] % 3;
            if ( i > 0  )
                res <<= 1;
        }
        return res;
    }
}