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    <p>Since your example method is tail-recursive, translating it to iterative style is easy and does not even require an explicit stack.</p> <p>Here are some steps that can be applied to any recursive function:</p> <p><strong>Step 1</strong>: Rewrite the method so it calls itself exactly once (your method already does this), has exactly one <code>return</code> statement, and uses <code>if</code> and <code>goto</code> instead of <code>else</code>, <code>while</code>, <code>for</code> and <code>foreach</code>:</p> <pre><code>int gcd(int m, int n) { int result; if (n == 0) { result = m; goto done; } result = gcd(n, m % n); done: return result; } </code></pre> <p><strong>Step 2</strong>: Replace the recursive call with the assignment of the new arguments to the parameters and a <code>goto</code> to the start of the method:</p> <pre><code>int gcd(int m, int n) { int result; start: if (n == 0) { result = m; goto done; } int old_m = m; m = n; n = old_m % n; goto start; done: return result; } </code></pre> <p>If the method was not tail-recursive, the method would need to save its state before the <code>goto</code> and restore it later again.</p> <p><strong>Step 3</strong>: Remove the <code>goto</code>s again:</p> <pre><code>int gcd(int m, int n) { int result; while (true) { if (n == 0) { result = m; break; } int old_m = m; m = n; n = old_m % n; } return result; } </code></pre> <p><strong>Step 4</strong>: Make the method look nicer:</p> <pre><code>int gcd(int m, int n) { while (n != 0) { int old_m = m; m = n; n = old_m % n; } return m; } </code></pre> <hr> <p>Here's an example that is not tail-recursive:</p> <pre><code>int fac(int x) { if (x == 0) { return 1; } return x * fac(x - 1); } </code></pre> <p><strong>Step 1:</strong></p> <pre><code>int fac(int x) { int result; if (x == 0) { result = 1; goto end; } result = x * fac(x - 1); end: return result; } </code></pre> <p><strong>Step 2:</strong></p> <pre><code>int fac(int x) { Stack&lt;int&gt; stack = new Stack&lt;int&gt;(); int result; start: if (x == 0) { result = 1; goto end; } stack.Push(x); x = x - 1; goto start; end: if (stack.Count != 0) { x = stack.Pop(); result = x * result; goto end; } return result; } </code></pre> <p><strong>Step 3:</strong></p> <pre><code>int fac(int x) { Stack&lt;int&gt; stack = new Stack&lt;int&gt;(); int result; while (true) { if (x == 0) { result = 1; break; } stack.Push(x); x = x - 1; } while (stack.Count != 0) { x = stack.Pop(); result = x * result; } return result; } </code></pre> <p><strong>Step 4:</strong></p> <pre><code>int fac(int x) { Stack&lt;int&gt; stack = new Stack&lt;int&gt;(); while (x != 0) { stack.Push(x); x = x - 1; } int result = 1; while (stack.Count != 0) { x = stack.Pop(); result = x * result; } return result; } </code></pre>
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