add python code

public/py/ch1/compare.py

@@ -0,0 +1,32 @@
+"""
+性能对比：循环累加 vs 高斯求和公式
+比较两种算法计算 1+2+...+n 的耗时差异
+"""
+import time
+
+def sum_by_loop(n):
+    """循环累加 O(n)"""
+    total = 0
+    for i in range(1, n + 1):
+        total += i
+    return total
+
+def sum_by_gauss(n):
+    """高斯求和公式 O(1)"""
+    return n * (n + 1) // 2
+
+# 测试不同规模
+for n in [1000, 10000, 100000, 1000000]:
+    print(f"\n--- n = {n} ---")
+
+    start = time.time()
+    r1 = sum_by_loop(n)
+    t1 = time.time() - start
+
+    start = time.time()
+    r2 = sum_by_gauss(n)
+    t2 = time.time() - start
+
+    print(f"循环累加: {t1:.6f} 秒, 结果 = {r1}")
+    print(f"高斯公式: {t2:.6f} 秒, 结果 = {r2}")
+    print(f"加速比: {t1/t2:.2f}x")