考虑数194声明为类型 INT 是否有可能得到它的数字的排列像其他有效的整数？ 编号：194 419 INT 491 INT 914 INT 941 INT

Consider number 194 declared as type int Is it possible to obtain it's digits permutations like other ints efficiently? Number: 194 419 int 491 int 914 int 941 int

我现在用的是next_permutation但它仅适用于数组。所以，我认为这将是不明智的INT转换为int数组（？！），然后得到排列为一个数组，并将其转换到它。

I am using the next_permutation however it only works with arrays. So I thought it wouldn't be wise to convert int to an int array (?!) then obtain the permutation as an array and convert it to it.

有什么建议？

推荐答案

置换的数字基本上是一个字符串操作，而不是一个（简单）的数学运算。转换到一个数组（字符串），然后用 next_permutation（）听起来不是试图数学上做更明智。

Permuting the digits is basically a string-operation, not a (simple) mathematical operation. Converting to an array (string) and then using next_permutation() sounds more sensible than trying to do it mathematically.

下面是数学版 - 没有保存的中间值：

Here's the mathematical version - without intermediate values saved:

int a = 194;
int b = (a / 100)       * 100 + (a % 10)        * 10 + ((a / 10) % 10) * 1; // 149
int c = (a % 10)        * 100 + ((a / 10) % 10) * 10 + (a / 100)       * 1; // 491
int d = (a % 10)        * 100 + (a / 100)       * 10 + ((a / 10) % 10) * 1; // 419
int e = ((a / 10) % 10) * 100 + (a / 100)       * 10 + (a % 10)        * 1; // 914
int f = ((a / 10) % 10) * 100 + (a % 10)        * 10 + (a / 100)       * 1; // 941

使用中间值，这是一个比较容易看到发生了什么事情（除了我通过产生不同硼分配 F 这个时候）。

With intermediate values, it's a little easier to see what's going on (except that I generated different assignments for b through f this time).

int a = 194;
int d1 = a / 100;
int d2 = (a / 10) % 10;
int d3 = a % 10;

int a = d1 * 100 + d2 * 10 + d3 * 1; // 194
int b = d1 * 100 + d3 * 10 + d2 * 1; // 149
int c = d2 * 100 + d1 * 10 + d3 * 1; // 914
int d = d2 * 100 + d3 * 10 + d1 * 1; // 941
int e = d3 * 100 + d1 * 10 + d2 * 1; // 419
int f = d3 * 100 + d2 * 10 + d1 * 1; // 491

使用了 next_permutation（）机制;它会推广到4位和第5位和N位数，其中该不会。

Use the next_permutation() mechanism; it will generalize to 4-digit and 5-digit and N-digit numbers where this will not.