Added Day1 to Day5 FastAPI assignments

Sandip/Day3.py

@@ -3,10 +3,12 @@
 
 app = FastAPI()
 
-@app.get("/")
-def home():
-    return {"message": "Server is running"}
+# GET API
+@app.get("/greet")
+def greet(name: str):
+    return {"message": f"Hello, {name}!"}
 
+# POST API
 class User(BaseModel):
     name: str
     age: int

Sandip/Day5.py

@@ -0,0 +1,34 @@
+from fastapi import FastAPI
+
+app = FastAPI()
+
+# Home
+@app.get("/")
+def home():
+    return {"message": "Calculator API is running"}
+
+# Add
+@app.get("/add")
+def add(a: int, b: int):
+    return {"result": a + b}
+
+# Subtract
+@app.get("/subtract")
+def subtract(a: int, b: int):
+    return {"result": a - b}
+
+# Multiply
+@app.get("/multiply")
+def multiply(a: int, b: int):
+    return {"result": a * b}
+
+# Divide
+@app.get("/divide")
+def divide(a: int, b: int):
+    if b == 0:
+        return {"error": "Cannot divide by zero"}
+    return {"result": a / b}
+
+@app.get("/square")
+def square(n: int):
+    return {"result": n * n}