How to Efficiently Extract Digits from an Integer into an Array?-C++-php.cn

How to Efficiently Extract Digits from an Integer into an Array?

Patricia Arquette

Release： 2025-01-12 16:22:43

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How to Efficiently Extract Digits from an Integer into an Array?

Efficiently Extract Integers into Arrays: A Concise Guide

Question:

Given an integer i, is there an efficient way to convert it into an array containing its individual numbers? For example, convert i = 987654321 to [9, 8, 7, 6, 5, 4, 3, 2, 1] without intermediate operations like ToString() and character iteration?

Answer:

Recursive solution using stack:

<code class="language-c#">public Stack<int> NumbersIn(int value)
{
    if (value == 0) return new Stack<int>();

    var numbers = NumbersIn(value / 10);

    numbers.Push(value % 10);

    return numbers;
}

var numbers = NumbersIn(987654321).ToArray();</code>

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Another solution using a for loop:

<code class="language-c#">public int[] NumbersIn(int value)
{
    var numbers = new Stack<int>();

    for(; value > 0; value /= 10)
        numbers.Push(value % 10);

    return numbers.ToArray();
}</code>

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Direct array-based method:

<code class="language-c#">private static int[] NumbersIn(int value)
{
  // 处理 value 为 0 或负数的特殊情况
  if (value == 0)
  {
    return new int[] { 0 };
  }

  value = Math.Abs(value);

  // 确定数字位数
  var digits = 1 + (int)Math.Log10(value);

  // 预分配数组
  var buffer = new int[digits];

  // 迭代并填充数组
  for (var counter = 0; counter < digits; counter++)
  {
    buffer[digits - 1 - counter] = value % 10;
    value /= 10;
  }

  return buffer;
}</code>

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These solutions provide efficient and concise ways to extract numbers from integers, allowing seamless conversion to arrays of individual numbers.

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