feat: add solutions for lc No.3120,3121 (#5191)

yanglbme · web-flow · commit 7833ad6726fb · 2026-05-08T08:36:14.000+08:00
diff --git a/solution/3100-3199/3120.Count the Number of Special Characters I/README.md b/solution/3100-3199/3120.Count the Number of Special Characters I/README.md
@@ -169,6 +169,26 @@ function numberOfSpecialChars(word: string): number {
 }
 ```
 
+#### Rust
+
+```rust
+impl Solution {
+    pub fn number_of_special_chars(word: String) -> i32 {
+        let mut s = [false; 128];
+        for ch in word.chars() {
+            s[ch as u8 as usize] = true;
+        }
+        let mut ans = 0;
+        for i in 0..26 {
+            if s[(b'a' + i) as usize] && s[(b'A' + i) as usize] {
+                ans += 1;
+            }
+        }
+        ans
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->
diff --git a/solution/3100-3199/3120.Count the Number of Special Characters I/README_EN.md b/solution/3100-3199/3120.Count the Number of Special Characters I/README_EN.md
@@ -167,6 +167,26 @@ function numberOfSpecialChars(word: string): number {
 }
 ```
 
+#### Rust
+
+```rust
+impl Solution {
+    pub fn number_of_special_chars(word: String) -> i32 {
+        let mut s = [false; 128];
+        for ch in word.chars() {
+            s[ch as u8 as usize] = true;
+        }
+        let mut ans = 0;
+        for i in 0..26 {
+            if s[(b'a' + i) as usize] && s[(b'A' + i) as usize] {
+                ans += 1;
+            }
+        }
+        ans
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->
diff --git a/solution/3100-3199/3120.Count the Number of Special Characters I/Solution.rs b/solution/3100-3199/3120.Count the Number of Special Characters I/Solution.rs
@@ -0,0 +1,15 @@
+impl Solution {
+    pub fn number_of_special_chars(word: String) -> i32 {
+        let mut s = [false; 128];
+        for ch in word.chars() {
+            s[ch as u8 as usize] = true;
+        }
+        let mut ans = 0;
+        for i in 0..26 {
+            if s[(b'a' + i) as usize] && s[(b'A' + i) as usize] {
+                ans += 1;
+            }
+        }
+        ans
+    }
+}
diff --git a/solution/3100-3199/3121.Count the Number of Special Characters II/README.md b/solution/3100-3199/3121.Count the Number of Special Characters II/README.md
@@ -120,7 +120,9 @@ class Solution {
         }
         int ans = 0;
         for (int i = 0; i < 26; ++i) {
-            if (last['a' + i] > 0 && first['A' + i] > 0 && last['a' + i] < first['A' + i]) {
+            int a = 'a' + i;
+            int b = 'A' + i;
+            if (last[a] > 0 && last[a] < first[b]) {
                 ++ans;
             }
         }
@@ -146,7 +148,7 @@ public:
         }
         int ans = 0;
         for (int i = 0; i < 26; ++i) {
-            if (last['a' + i] && first['A' + i] && last['a' + i] < first['A' + i]) {
+            if (last['a' + i] && last['a' + i] < first['A' + i]) {
                 ++ans;
             }
         }
@@ -168,7 +170,7 @@ func numberOfSpecialChars(word string) (ans int) {
 		last[c] = i + 1
 	}
 	for i := 0; i < 26; i++ {
-		if last['a'+i] > 0 && first['A'+i] > 0 && last['a'+i] < first['A'+i] {
+		if last['a'+i] > 0 && last['a'+i] < first['A'+i] {
 			ans++
 		}
 	}
@@ -191,18 +193,44 @@ function numberOfSpecialChars(word: string): number {
     }
     let ans: number = 0;
     for (let i = 0; i < 26; ++i) {
-        if (
-            last['a'.charCodeAt(0) + i] &&
-            first['A'.charCodeAt(0) + i] &&
-            last['a'.charCodeAt(0) + i] < first['A'.charCodeAt(0) + i]
-        ) {
+        const a = 'a'.charCodeAt(0) + i;
+        const b = 'A'.charCodeAt(0) + i;
+        if (last[a] && last[a] < first[b]) {
             ++ans;
         }
     }
     return ans;
 }
 ```
 
+#### Rust
+
+```rust
+impl Solution {
+    pub fn number_of_special_chars(word: String) -> i32 {
+        let mut first = [0; 128];
+        let mut last = [0; 128];
+        for (i, ch) in word.chars().enumerate() {
+            let j = ch as u8 as usize;
+            let pos = (i + 1) as i32;
+            if first[j] == 0 {
+                first[j] = pos;
+            }
+            last[j] = pos;
+        }
+        let mut ans = 0;
+        for i in 0..26 {
+            let a = (b'a' + i) as usize;
+            let b = (b'A' + i) as usize;
+            if last[a] > 0 && last[a] < first[b] {
+                ans += 1;
+            }
+        }
+        ans
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->
diff --git a/solution/3100-3199/3121.Count the Number of Special Characters II/README_EN.md b/solution/3100-3199/3121.Count the Number of Special Characters II/README_EN.md
@@ -118,7 +118,9 @@ class Solution {
         }
         int ans = 0;
         for (int i = 0; i < 26; ++i) {
-            if (last['a' + i] > 0 && first['A' + i] > 0 && last['a' + i] < first['A' + i]) {
+            int a = 'a' + i;
+            int b = 'A' + i;
+            if (last[a] > 0 && last[a] < first[b]) {
                 ++ans;
             }
         }
@@ -144,7 +146,7 @@ public:
         }
         int ans = 0;
         for (int i = 0; i < 26; ++i) {
-            if (last['a' + i] && first['A' + i] && last['a' + i] < first['A' + i]) {
+            if (last['a' + i] && last['a' + i] < first['A' + i]) {
                 ++ans;
             }
         }
@@ -166,7 +168,7 @@ func numberOfSpecialChars(word string) (ans int) {
 		last[c] = i + 1
 	}
 	for i := 0; i < 26; i++ {
-		if last['a'+i] > 0 && first['A'+i] > 0 && last['a'+i] < first['A'+i] {
+		if last['a'+i] > 0 && last['a'+i] < first['A'+i] {
 			ans++
 		}
 	}
@@ -189,18 +191,44 @@ function numberOfSpecialChars(word: string): number {
     }
     let ans: number = 0;
     for (let i = 0; i < 26; ++i) {
-        if (
-            last['a'.charCodeAt(0) + i] &&
-            first['A'.charCodeAt(0) + i] &&
-            last['a'.charCodeAt(0) + i] < first['A'.charCodeAt(0) + i]
-        ) {
+        const a = 'a'.charCodeAt(0) + i;
+        const b = 'A'.charCodeAt(0) + i;
+        if (last[a] && last[a] < first[b]) {
             ++ans;
         }
     }
     return ans;
 }
 ```
 
+#### Rust
+
+```rust
+impl Solution {
+    pub fn number_of_special_chars(word: String) -> i32 {
+        let mut first = [0; 128];
+        let mut last = [0; 128];
+        for (i, ch) in word.chars().enumerate() {
+            let j = ch as u8 as usize;
+            let pos = (i + 1) as i32;
+            if first[j] == 0 {
+                first[j] = pos;
+            }
+            last[j] = pos;
+        }
+        let mut ans = 0;
+        for i in 0..26 {
+            let a = (b'a' + i) as usize;
+            let b = (b'A' + i) as usize;
+            if last[a] > 0 && last[a] < first[b] {
+                ans += 1;
+            }
+        }
+        ans
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->
diff --git a/solution/3100-3199/3121.Count the Number of Special Characters II/Solution.cpp b/solution/3100-3199/3121.Count the Number of Special Characters II/Solution.cpp
@@ -12,10 +12,10 @@ class Solution {
         }
         int ans = 0;
         for (int i = 0; i < 26; ++i) {
-            if (last['a' + i] && first['A' + i] && last['a' + i] < first['A' + i]) {
+            if (last['a' + i] && last['a' + i] < first['A' + i]) {
                 ++ans;
             }
         }
         return ans;
     }
-};
+};
diff --git a/solution/3100-3199/3121.Count the Number of Special Characters II/Solution.go b/solution/3100-3199/3121.Count the Number of Special Characters II/Solution.go
@@ -8,9 +8,9 @@ func numberOfSpecialChars(word string) (ans int) {
 		last[c] = i + 1
 	}
 	for i := 0; i < 26; i++ {
-		if last['a'+i] > 0 && first['A'+i] > 0 && last['a'+i] < first['A'+i] {
+		if last['a'+i] > 0 && last['a'+i] < first['A'+i] {
 			ans++
 		}
 	}
 	return
-}
+}
diff --git a/solution/3100-3199/3121.Count the Number of Special Characters II/Solution.java b/solution/3100-3199/3121.Count the Number of Special Characters II/Solution.java
@@ -11,10 +11,12 @@ public int numberOfSpecialChars(String word) {
         }
         int ans = 0;
         for (int i = 0; i < 26; ++i) {
-            if (last['a' + i] > 0 && first['A' + i] > 0 && last['a' + i] < first['A' + i]) {
+            int a = 'a' + i;
+            int b = 'A' + i;
+            if (last[a] > 0 && last[a] < first[b]) {
                 ++ans;
             }
         }
         return ans;
     }
-}
+}
diff --git a/solution/3100-3199/3121.Count the Number of Special Characters II/Solution.rs b/solution/3100-3199/3121.Count the Number of Special Characters II/Solution.rs
@@ -0,0 +1,23 @@
+impl Solution {
+    pub fn number_of_special_chars(word: String) -> i32 {
+        let mut first = [0; 128];
+        let mut last = [0; 128];
+        for (i, ch) in word.chars().enumerate() {
+            let j = ch as u8 as usize;
+            let pos = (i + 1) as i32;
+            if first[j] == 0 {
+                first[j] = pos;
+            }
+            last[j] = pos;
+        }
+        let mut ans = 0;
+        for i in 0..26 {
+            let a = (b'a' + i) as usize;
+            let b = (b'A' + i) as usize;
+            if last[a] > 0 && last[a] < first[b] {
+                ans += 1;
+            }
+        }
+        ans
+    }
+}
diff --git a/solution/3100-3199/3121.Count the Number of Special Characters II/Solution.ts b/solution/3100-3199/3121.Count the Number of Special Characters II/Solution.ts
@@ -10,11 +10,9 @@ function numberOfSpecialChars(word: string): number {
     }
     let ans: number = 0;
     for (let i = 0; i < 26; ++i) {
-        if (
-            last['a'.charCodeAt(0) + i] &&
-            first['A'.charCodeAt(0) + i] &&
-            last['a'.charCodeAt(0) + i] < first['A'.charCodeAt(0) + i]
-        ) {
+        const a = 'a'.charCodeAt(0) + i;
+        const b = 'A'.charCodeAt(0) + i;
+        if (last[a] && last[a] < first[b]) {
             ++ans;
         }
     }

Original file line number	Diff line number	Diff line change
`@@ -12,10 +12,10 @@ class Solution {`
`12`	`12`	`}`
`13`	`13`	`int ans = 0;`
`14`	`14`	`for (int i = 0; i < 26; ++i) {`
`15`		`- if (last['a' + i] && first['A' + i] && last['a' + i] < first['A' + i]) {`
	`15`	`+ if (last['a' + i] && last['a' + i] < first['A' + i]) {`
`16`	`16`	`++ans;`
`17`	`17`	`}`
`18`	`18`	`}`
`19`	`19`	`return ans;`
`20`	`20`	`}`
`21`		`-};`
	`21`	`+};`
Original file line number	Diff line number	Diff line change
`@@ -8,9 +8,9 @@ func numberOfSpecialChars(word string) (ans int) {`
`8`	`8`	`last[c] = i + 1`
`9`	`9`	`}`
`10`	`10`	`for i := 0; i < 26; i++ {`
`11`		`- if last['a'+i] > 0 && first['A'+i] > 0 && last['a'+i] < first['A'+i] {`
	`11`	`+ if last['a'+i] > 0 && last['a'+i] < first['A'+i] {`
`12`	`12`	`ans++`
`13`	`13`	`}`
`14`	`14`	`}`
`15`	`15`	`return`
`16`		`-}`
	`16`	`+}`
Original file line number	Diff line number	Diff line change
`@@ -11,10 +11,12 @@ public int numberOfSpecialChars(String word) {`
`11`	`11`	`}`
`12`	`12`	`int ans = 0;`
`13`	`13`	`for (int i = 0; i < 26; ++i) {`
`14`		`- if (last['a' + i] > 0 && first['A' + i] > 0 && last['a' + i] < first['A' + i]) {`
	`14`	`+ int a = 'a' + i;`
	`15`	`+ int b = 'A' + i;`
	`16`	`+ if (last[a] > 0 && last[a] < first[b]) {`
`15`	`17`	`++ans;`
`16`	`18`	`}`
`17`	`19`	`}`
`18`	`20`	`return ans;`
`19`	`21`	`}`
`20`		`-}`
	`22`	`+}`
Original file line number	Diff line number	Diff line change
`@@ -10,11 +10,9 @@ function numberOfSpecialChars(word: string): number {`
`10`	`10`	`}`
`11`	`11`	`let ans: number = 0;`
`12`	`12`	`for (let i = 0; i < 26; ++i) {`
`13`		`- if (`
`14`		`- last['a'.charCodeAt(0) + i] &&`
`15`		`- first['A'.charCodeAt(0) + i] &&`
`16`		`- last['a'.charCodeAt(0) + i] < first['A'.charCodeAt(0) + i]`
`17`		`- ) {`
	`13`	`+ const a = 'a'.charCodeAt(0) + i;`
	`14`	`+ const b = 'A'.charCodeAt(0) + i;`
	`15`	`+ if (last[a] && last[a] < first[b]) {`
`18`	`16`	`++ans;`
`19`	`17`	`}`
`20`	`18`	`}`