feat: add pandas solution to lc problem: No.0550 (doocs#1891)

* Solution for 511.

* Solution for 550.

* Update README.md

* Update README_EN.md

* Update Solution.py

* Update Solution.py

* Update README_EN.md

* Update README.md

Author: nrhitik

solution/0500-0599/0550.Game Play Analysis IV/README.md

@@ -107,4 +107,22 @@ FROM T
 WHERE rk = 1;
 ```
 
+### **Pandas**
+
+```python
+import pandas as pd
+
+
+def gameplay_analysis(activity: pd.DataFrame) -> pd.DataFrame:
+    activity["first"] = activity.groupby("player_id").event_date.transform(min)
+    activity_2nd_day = activity[
+        activity["first"] + pd.DateOffset(1) == activity["event_date"]
+    ]
+
+    return pd.DataFrame(
+        {"fraction": [round(len(activity_2nd_day) / activity.player_id.nunique(), 2)]}
+    )
+
+```
+
 <!-- tabs:end -->

solution/0500-0599/0550.Game Play Analysis IV/README_EN.md

@@ -102,4 +102,22 @@ FROM T
 WHERE rk = 1;
 ```
 
+### **Pandas**
+
+```python
+import pandas as pd
+
+
+def gameplay_analysis(activity: pd.DataFrame) -> pd.DataFrame:
+    activity["first"] = activity.groupby("player_id").event_date.transform(min)
+    activity_2nd_day = activity[
+        activity["first"] + pd.DateOffset(1) == activity["event_date"]
+    ]
+
+    return pd.DataFrame(
+        {"fraction": [round(len(activity_2nd_day) / activity.player_id.nunique(), 2)]}
+    )
+
+```
+
 <!-- tabs:end -->

solution/0500-0599/0550.Game Play Analysis IV/Solution.py

@@ -0,0 +1,12 @@
+import pandas as pd
+
+
+def gameplay_analysis(activity: pd.DataFrame) -> pd.DataFrame:
+    activity["first"] = activity.groupby("player_id").event_date.transform(min)
+    activity_2nd_day = activity[
+        activity["first"] + pd.DateOffset(1) == activity["event_date"]
+    ]
+
+    return pd.DataFrame(
+        {"fraction": [round(len(activity_2nd_day) / activity.player_id.nunique(), 2)]}
+    )