Initial commit: C language learning code

翁凯C语言/2/素数判断3.c

@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <math.h>
+
+// !素数判断的简化版本
+int sushu(int x)
+{
+	int ret = 1;
+
+	if (x <= 1) 
+	{
+		ret = 0;
+	}
+
+	int i;
+	if (x == 2 || (x % 2 == 0 && x != 2))	// 排除偶数
+	{
+		ret = 0;
+	}
+	for (i = 3; i < (int)sqrt(x)+1; i += 2)
+	{
+		if (x % i == 0)
+		{
+			ret = 0;
+			break;
+		}
+	}
+	
+	return ret;
+}
+
+int main()
+{
+	int x;
+	printf("输入数字：");
+	scanf("%d", &x);
+
+	if (sushu(x))
+	{
+		printf("%d是素数\n", x);
+	}
+	else
+	{
+		printf("%d不是素数\n", x);
+	}
+
+	return 0;
+}