Remove k-elemnts

Remove k-elemnts/Solution.java

@@ -0,0 +1,44 @@
+class Solution {
+    public String removeKdigits(String num, int k) 
+    {
+        if(k == num.length())
+            return "0";
+
+        Stack<Character> stack = new Stack<>();
+
+        int i=0;
+
+        while(i < num.length())
+        {
+            char ch = num.charAt(i);
+            //whenever meet a digit which is less than the previous digit, discard the previous one
+            while(!stack.isEmpty() && stack.peek() > ch && k > 0)
+            {
+                stack.pop();
+                k--;
+            }
+            stack.push(ch);
+            i++;
+        }
+        //for corner case like 1111
+        while(k > 0)
+        {
+            stack.pop();
+            k--;
+        }
+
+        //constructing number from stack
+
+        StringBuilder sb = new StringBuilder();
+
+        while(!stack.isEmpty())
+            sb.append(stack.pop());
+
+        sb.reverse();
+
+        while(sb.charAt(0) == '0' && sb.length() > 1)
+            sb.deleteCharAt(0);
+
+        return sb.toString();
+    }
+}