From aaa8cc2443a9a05e5af3acae67d7f593c7c34077 Mon Sep 17 00:00:00 2001
From: fwqaaq <fwqaaq@gmail.com>
Date: Sun, 23 Jul 2023 19:40:19 +0800
Subject: [PATCH] =?UTF-8?q?Update=200115.=E4=B8=8D=E5=90=8C=E7=9A=84?=
 =?UTF-8?q?=E5=AD=90=E5=BA=8F=E5=88=97.md?=
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---
 problems/0115.不同的子序列.md | 30 +++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/problems/0115.不同的子序列.md b/problems/0115.不同的子序列.md
index 56516132..91f35291 100644
--- a/problems/0115.不同的子序列.md
+++ b/problems/0115.不同的子序列.md
@@ -337,6 +337,36 @@ impl Solution {
 }
 ```
 
+> 滚动数组
+
+```rust
+impl Solution {
+    pub fn num_distinct(s: String, t: String) -> i32 {
+        if s.len() < t.len() {
+            return 0;
+        }
+        let (s, t) = (s.into_bytes(), t.into_bytes());
+        // 对于 t 为空字符串，s 作为子序列的个数为 1（删除 s 所有元素）
+        let mut dp = vec![1; s.len() + 1];
+        for char_t in t {
+            // dp[i - 1][j - 1]，dp[j + 1] 更新之前的值
+            let mut pre = dp[0];
+            // 当开始遍历 t，s 的前 0 个字符无法包含任意子序列
+            dp[0] = 0;
+            for (j, &char_s) in s.iter().enumerate() {
+                let temp = dp[j + 1];
+                if char_t == char_s {
+                    dp[j + 1] = pre + dp[j];
+                } else {
+                    dp[j + 1] = dp[j];
+                }
+                pre = temp;
+            }
+        }
+        dp[s.len()]
+    }
+}
+```
 
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