From 5b692968a99d98c7dd5a54af7015f5a9e0d06d19 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=98=93=E6=98=A5=E9=A3=8E?=
 <77157236+night-cruise@users.noreply.github.com>
Date: Fri, 29 Sep 2023 12:17:05 +0800
Subject: [PATCH] feat: add for-loop-recur rust codes (#803)

---
 .../recursion.rs                              | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/codes/rust/chapter_computational_complexity/recursion.rs b/codes/rust/chapter_computational_complexity/recursion.rs
index d8c2a8d7f..9f4826bcd 100644
--- a/codes/rust/chapter_computational_complexity/recursion.rs
+++ b/codes/rust/chapter_computational_complexity/recursion.rs
@@ -17,6 +17,25 @@ fn recur(n: i32) -> i32 {
     n + res
 }
 
+/* 使用迭代模拟递归 */
+fn for_loop_recur(n: i32) -> i32 {
+    // 使用一个显式的栈来模拟系统调用栈
+    let mut stack = Vec::new();
+    let mut res = 0;
+    // 递：递归调用
+    for i in (1..=n).rev() {
+        // 通过“入栈操作”模拟“递”
+        stack.push(i);
+    }
+    // 归：返回结果
+    while !stack.is_empty() {
+        // 通过“出栈操作”模拟“归”
+        res += stack.pop().unwrap();
+    }
+    // res = 1+2+3+...+n
+    res
+}
+
 /* 尾递归 */
 fn tail_recur(n: i32, res: i32) -> i32 {
     // 终止条件
@@ -47,6 +66,9 @@ fn main() {
     res = recur(n);
     println!("\n递归函数的求和结果 res = {res}");
 
+    res = for_loop_recur(n);
+    println!("\n使用迭代模拟递归求和结果 res = {res}");
+
     res = tail_recur(n, 0);
     println!("\n尾递归函数的求和结果 res = {res}");