'commit'

TangDou/LuoGuBook/P1217_1.cpp

@@ -0,0 +1,33 @@
+#include<bits/stdc++.h>
+
+using namespace std;
+const int N = 1e8 + 10;
+int primes[N], cnt;
+bool st[N];
+void get_primes(int n) {
+    for (int i = 2; i <= n; i++) {
+        if (!st[i]) primes[cnt++] = i;
+        for (int j = 0; primes[j] <= n / i; j++) {
+            st[primes[j] * i] = true;
+            if (i % primes[j] == 0) break;
+        }
+    }
+}
+bool isHWS(int num) {
+    int t = num, ans = 0;
+    while (t) {
+        ans = ans * 10 + t % 10;
+        t /= 10;
+    }
+    return ans == num;
+}
+int main() {
+    int a, b;
+    cin >> a >> b;
+    if (b >= 1e7) b = 1e7;
+    get_primes(b);
+    for (int i = a; i <= b; i++)
+        if (!st[i] && isHWS(i))
+            cout << i << endl;
+    return 0;
+}