add 素数筛.

utils/cal_prime.py

@@ -0,0 +1,15 @@
+def cal_prime(n):
+    prime = [1] * (n + 1)
+    prime[0] = prime[1] = 0
+    for i in range(2, n + 1):
+        j = i * i
+        while j <= n:
+            prime[j] = 0
+            j += i
+
+    res = []
+    for idx, num in enumerate(prime):
+        if num:
+            res.append(idx)
+
+    return res