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素数判断..cpp

@@ -0,0 +1,21 @@
+#include<stdio.h>
+#include<math.h>
+ 
+int main()
+{
+    int i, n, k;
+ 
+    scanf("%d", &n);
+    k = sqrt(n + 1);
+ 
+    for(i = 2; i <= k; i++) 
+        if(n % i == 0) 
+            break;
+ 
+    if(i <= k || n == 1)
+        printf("No\n");
+    else
+        printf("Yes\n");
+ 
+    return 0;
+}