判斷一個數是不是2的N次方，很牛的算法#define ISPOW2(x) (x) & (x-1) ? false : true

原創 xuxiake2012 2020-02-21 00:56

判斷一個數是不是2的N次方，很牛的算法#define ISPOW2(x)   (x) & (x-1) ? false : true

原理：由於2的N次方的數二進制表示是第1位爲1，其餘爲0，而x-1（假如x爲2的N次方）得到的數的二進制表示恰恰是第1位爲0，其餘爲1，兩者相與，得到的結果就爲0，否則結果肯定不爲0
 

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