Integer Reversal (Go, LeetCode)

table of Contents

Title description

solution

Code

Code walkthrough

Portal

---

 

Title description

Given a 32-bit signed integer, you need to invert the digits on each bit of the integer. For overflowing 32-bit numbers, 0 is returned.

Input/output description

enter	321
Output	123

 

solution

The topic is relatively simple, and you need to pay attention to two places:

• The number entered may be negative. Negative number is still negative after reversal
• If the inverted number exceeds 32 bits, it needs to return 0

 

Code

package main

import "strconv"

func reverse(x int) int {
	positive := true
	if x < 0 {
		positive = false
		x = -x
	}

	xStr := strconv.Itoa(x)
	resultStr := ""
	for i := len(xStr) - 1; i >= 0; i-- {
		resultStr += string(xStr[i])
	}

	result, _ := strconv.Atoi(resultStr)
	if !positive {
		result = -result
	}

	if result < -(1<<31) || result > (1<<31)-1 {
		result = 0
	}
	return result
}

 

Code walkthrough

package main

import "strconv"

func reverse(x int) int {
   // 先判断x的正负性。记录后将x统一转换为正数（方便逆序）
   positive := true
   if x < 0 {
      positive = false
      x = -x
   }

   // 将x转换为字符串逆序，得到逆序后的字符串
   xStr := strconv.Itoa(x)
   resultStr := ""
   for i := len(xStr) - 1; i >= 0; i-- {
      resultStr += string(xStr[i])
   }

   // 根据先前记录的正负性，将逆序后的字符串还原为整数结果
   result, _ := strconv.Atoi(resultStr)
   if !positive {
      result = -result
   }

   // 判断是否溢出32位
   if result < -(1<<31) || result > (1<<31)-1 {
      result = 0
   }
   return result
}

 

Portal

LeetCode test question link