Create 3614.Process-String-with-Special-Operations-II.cpp

Author: wisdompeak

Recursion/3614.Process-String-with-Special-Operations-II/3614.Process-String-with-Special-Operations-II.cpp

@@ -0,0 +1,46 @@
+using ll = long long;
+class Solution {
+public:
+    char processStr(string s, long long k) {
+        k++;
+        int n = s.size();
+        s = "#"+s;
+        vector<ll>len(n+1);
+        const ll INF = 1e15+5;
+
+        for (int i=1; i<=n; i++) {
+            char c = s[i];
+            ll prev = len[i-1];
+            ll now = prev;
+            if ('a'<=c && c<='z')
+                now = prev+1;
+            else if (c == '*')
+                now = prev>0 ? (prev-1): 0;
+            else if (c=='#')
+                now = prev*2;
+            else if (c=='%')
+                now = prev;
+            len[i] = min(now, INF);                   
+        }
+        if (k==0 || k>(ll)len[n]) return '.';
+
+        for (int i=n; i>=1; i--) {
+            char c = s[i];
+            ll before = len[i-1];
+            ll after = len[i];
+            if ('a'<=c && c<='z') {
+                if (k==after)
+                    return c;
+            } else if (c=='*') {
+                
+            } else if (c=='#') {
+                if (k>before)
+                    k-=before;
+            } else if ( c=='%') {
+                k = before-k+1;
+            }
+        }
+
+        return '.';
+    }
+};