删除整数中的重复数字 [英] Removing duplicate digits in an integer

问题描述

我已经在技术方面遇到了这个程序.他们给了我这个程序，用于删除给定整数中的重复数字，而无需使用数组或字符串.

I have faced this program in technical round. They have give this program to me for removing duplicate digits in given integer without using arrays or strings.

示例:

int i = 123134254;

预期输出:12345

推荐答案

您可以使用int作为集合，通过分配每个数字(0、1、2，...来存储已经遇到的数字). ，9)表示int.然后，您可以遍历i的数字并通过参考此集合来建立新的唯一数字位数.请注意，我首先反转了i的数字，以便可以按顺序轻松地对其进行循环:

You can use an int as a set to store the digits you've already encountered by assigning each digit (0,1,2,...,9) to a bit of said int. You can then loop over the digits of i and build a new number of solely unique digits by consulting this set. Note that I first reverse the digits of i so I can easily loop over them in-order:

int i = 123134254;
int res = 0;  // result

int set = 0;  // digits we've seen
int rev = 0;  // digits of `i` reversed

while (i > 0) {
    rev = (rev * 10) + (i % 10);
    i /= 10;
}

while (rev > 0) {
    final int mod = rev % 10;
    final int mask = 1 << mod;
    if ((set & mask) == 0) {
        res = (res * 10) + mod;
        set |= mask;
    }
    rev /= 10;
}

System.out.println(res);

12345

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