feat: add rust solution to lc problem: No.2678 (#1087)

Author: dierbei

solution/2600-2699/2678.Number of Senior Citizens/README.md

@@ -120,6 +120,38 @@ func countSeniors(details []string) (ans int) {
 }
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    pub fn count_seniors(details: Vec<String>) -> i32 {
+        let mut ans = 0;
+
+        for s in details.iter() {
+            if let Ok(age) = s[11..13].parse::<i32>() {
+                if age > 60 {
+                    ans += 1;
+                }
+            }
+        }
+
+        ans
+    }
+}
+```
+
+```rust
+impl Solution {
+    pub fn count_seniors(details: Vec<String>) -> i32 {
+        details
+            .iter()
+            .filter_map(|s| s[11..13].parse::<i32>().ok())
+            .filter(|&age| age > 60)
+            .count() as i32
+    }
+}
+```
+
 ### **...**
 
 ```

solution/2600-2699/2678.Number of Senior Citizens/README_EN.md

@@ -102,6 +102,38 @@ func countSeniors(details []string) (ans int) {
 }
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    pub fn count_seniors(details: Vec<String>) -> i32 {
+        let mut ans = 0;
+
+        for s in details.iter() {
+            if let Ok(age) = s[11..13].parse::<i32>() {
+                if age > 60 {
+                    ans += 1;
+                }
+            }
+        }
+
+        ans
+    }
+}
+```
+
+```rust
+impl Solution {
+    pub fn count_seniors(details: Vec<String>) -> i32 {
+        details
+            .iter()
+            .filter_map(|s| s[11..13].parse::<i32>().ok())
+            .filter(|&age| age > 60)
+            .count() as i32
+    }
+}
+```
+
 ### **...**
 
 ```

solution/2600-2699/2678.Number of Senior Citizens/Solution.rs

@@ -0,0 +1,15 @@
+impl Solution {
+    pub fn count_seniors(details: Vec<String>) -> i32 {
+        let mut ans = 0;
+
+        for s in details.iter() {
+            if let Ok(age) = s[11..13].parse::<i32>() {
+                if age > 60 {
+                    ans += 1;
+                }
+            }
+        }
+
+        ans
+    }
+}