Update readme.md

Co-Authored-By: Antim-IWP <[email protected]>
Co-Authored-By: Shiwangi Srivastava <[email protected]>

Author: 3 people

Solution/2390. Removing Stars From a String/readme.md

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+# 2390. Removing Stars From a String
+
+> Difficulty: Medium  
+> Source: [LeetCode](https://leetcode.com/problems/removing-stars-from-a-string)  
+> Tags: Stack, String, Simulation
+
+## Description
+
+You are given a string `s`, which contains stars `*`.
+
+In one operation, you can:
+- Choose a star in `s`.
+- Remove the closest **non-star** character to its **left**, as well as remove the star itself.
+
+Return *the string after all stars have been removed*.
+
+**Note:**
+- The input will be generated such that the operation is always possible.
+- It can be shown that the resulting string will always be unique.
+
+---
+
+## Examples
+
+### Example 1:
+```
+Input: s = "leet**cod*e"
+Output: "lecoe"
+Explanation: Performing the removals from left to right:
+- The closest character to the 1st star is 't' -> "lee*cod*e"
+- Then remove 'e' -> "lecod*e"
+- Then remove 'd' -> "lecoe"
+```
+
+### Example 2:
+```
+Input: s = "erase*****"
+Output: ""
+Explanation: All characters are removed.
+```
+
+---
+
+## Constraints
+
+- `1 <= s.length <= 10⁵`
+- `s` consists of lowercase English letters and stars `*`.
+- The operation above can be performed on `s`.
+
+---
+
+## Solution
+
+### Approach: Stack Simulation
+
+We simulate the removal process using a stack:
+- Iterate through the string `s`.
+- Push characters onto a stack until you encounter a `*`.
+- When a `*` is found, pop the top character from the stack (removing the left character).
+
+### Time and Space Complexity
+
+- **Time Complexity:** O(n)  
+- **Space Complexity:** O(n) in the worst case (when no `*` are present)
+
+---
+
+## Code
+
+### Python
+
+```python
+class Solution:
+    def removeStars(self, s: str) -> str:
+        ans = []
+        for c in s:
+            if c == '*':
+                ans.pop()
+            else:
+                ans.append(c)
+        return ''.join(ans)
+```
+
+### Java
+
+```java
+class Solution {
+    public String removeStars(String s) {
+        StringBuilder ans = new StringBuilder();
+        for (char c : s.toCharArray()) {
+            if (c == '*') {
+                ans.deleteCharAt(ans.length() - 1);
+            } else {
+                ans.append(c);
+            }
+        }
+        return ans.toString();
+    }
+}
+```
+
+### C++
+
+```cpp
+class Solution {
+public:
+    string removeStars(string s) {
+        string ans;
+        for (char c : s) {
+            if (c == '*') {
+                ans.pop_back();
+            } else {
+                ans.push_back(c);
+            }
+        }
+        return ans;
+    }
+};
+```
+
+### Go
+
+```go
+func removeStars(s string) string {
+	ans := []rune{}
+	for _, c := range s {
+		if c == '*' {
+			ans = ans[:len(ans)-1]
+		} else {
+			ans = append(ans, c)
+		}
+	}
+	return string(ans)
+}
+```
+
+### TypeScript
+
+```ts
+function removeStars(s: string): string {
+    const ans: string[] = [];
+    for (const c of s) {
+        if (c === '*') {
+            ans.pop();
+        } else {
+            ans.push(c);
+        }
+    }
+    return ans.join('');
+}
+```
+
+### Rust
+
+```rust
+impl Solution {
+    pub fn remove_stars(s: String) -> String {
+        let mut ans = String::new();
+        for c in s.chars() {
+            if c == '*' {
+                ans.pop();
+            } else {
+                ans.push(c);
+            }
+        }
+        ans
+    }
+}
+```
+
+### PHP
+
+```php
+class Solution {
+    function removeStars($s) {
+        $stack = [];
+        for ($i = 0; $i < strlen($s); $i++) {
+            if ($s[$i] === '*') {
+                array_pop($stack);
+            } else {
+                $stack[] = $s[$i];
+            }
+        }
+        return implode('', $stack);
+    }
+}
+```
+