[feat ]: leetcode 402

Author: BWbwchen

leetcode/0402_Remove-K-Digits.rs

@@ -0,0 +1,28 @@
+impl Solution {
+    pub fn remove_kdigits(num: String, k: i32) -> String {
+        use std::collections::VecDeque;
+        let mut k = k;
+        let mut mstack:Vec<char> = Vec::new();
+        // Monolitic stack
+        for n in num.chars() {
+            // insert to stack
+            while !mstack.is_empty() && k > 0 && *mstack.last().unwrap() > n {
+                mstack.pop();
+                k -= 1;
+            }
+            mstack.push(n);
+        }
+
+        for _ in 0..k {
+            mstack.pop();
+        }
+
+        let ret = mstack.into_iter().collect::<String>().trim_start_matches('0').to_string();
+
+        if ret.len() == 0 {
+            "0".to_string()
+        } else {
+            ret
+        }
+    }
+}