007ReverseInteger.md

Reverse Integer

Description

Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

Input: 123
Output:  321

Example 2:

Input: -123
Output: -321

Example 3:

Input: 120
Output: 21

Note:

Assume we are dealing with an environment which could only hold integers within the 32-bit signed integer range. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

Tags: Math

思路

题意是给你一个整型数，求它的逆序整型数，而且有个小坑点，当它的逆序整型数溢出的话，那么就返回 0，用我们代码表示的话可以求得结果保存在 long 中，最后把结果和整型的两个范围比较即可。

func reverseInteger(_ x: Int) -> Int {
    var result:Int64 = 0;
    var input = x;
    
    while input != 0 {
        result = result * 10 + (Int64)(input % 10);
        input = input / 10;
    }
    
    return (result > Int32.max || result < Int32.min) ? 0 : Int(result)
}

let input = 123
print(" Input: '\(input)', Output: '\(reverseInteger(input))'")

结语

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