Create 440. K-th Smallest in Lexicographical Order (#812)

Author: Chayandas07

440. K-th Smallest in Lexicographical Order

@@ -0,0 +1,32 @@
+class Solution {
+public:
+    #define ll long long
+    int countsteps(int n,int k,ll prefix1,ll prefix2){
+        int steps=0;
+        while(prefix1<=n){
+            steps+=min(1LL*(n+1),prefix2)-prefix1;
+            prefix1*=10;
+            prefix2*=10;
+
+        }
+        return steps;
+    }
+    int findKthNumber(int n, int k) {
+        ll curr=1;
+        k-=1;
+
+        while(k!=0){
+            int steps=countsteps(n,k,curr,curr+1);
+            if(steps<=k){
+                curr++;
+                k-=steps;
+            }else{
+                curr*=10;
+                k--;
+            }
+
+        }
+        return curr;
+
+    }
+};