Question

Java中是否有内置函数可用于交换两位？

例如：

_ _ _ _ 1 _ _ 0位3与位0交换并变为_ _ _ _ 0 _ _ 1

我知道可以使用逐位操作的长程序来完成，但我想避免这样做。

Answer 1

您也可以尝试这种方式

//positions are indexed from 0 and in order ...[4][3][2][1][0]
//so changing 3 and 1 will make             ...[4][1][2][3][0]
public static int swap(int i, int pos1, int pos2) {

    int bit1 = (i >> pos1) & 1;// bit at pos1
    int bit2 = (i >> pos2) & 1;// bit at pos2

    if (bit1 == bit2)
        return i; // no need to swap since we change 1 with 1 or 0 with 0

    // Since we are here it means that we need to change 1->0 and 0->1.
    // To do this we can use XOR (^).
    // Lets create mask 000001010 with ones at specified positions
    int mask = (1 << pos1) | (1 << pos2);

    return i ^ mask;// TADAM!!!
}

Answer 2

这是一种替代方式，称为delta-swap。

int t = (i ^ (i >> 3)) & 1;
return i ^ t ^ (t << 3);

或更一般地说：

static int swap(int x, int i, int j)
{
    // precondition: i > j
    int d = i - j;
    int y = (x ^ (x >> d)) & (1 << j);
    return x ^ y ^ (y << d);
}

Answer 3

我正在制作详细信息，但您可以将其加入单行

 int temp1 = (i & 0x1) << 3; //extract lowest bit #1 and place at pos# 4
 int temp2 = (i & 0x8) >> 3; //extract bit #4 and place at pos #1
 i = (i & temp1) | (i & ~temp1); //now pos #4 is ready     
 i = (i & temp2) | (i & ~temp2); //now pos #1 is ready

如何在Java中交换两位整数？

3 个答案: