'commit'

TangDou/LuoGuBook/P1217_2.cpp

@@ -0,0 +1,39 @@
+#include<bits/stdc++.h>
+
+using namespace std;
+const int N = 100000010;
+
+//欧拉筛
+int primes[N], cnt;     // primes[]存储所有素数
+bool st[N];             // st[x]存储x是否被筛掉
+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;
+        }
+    }
+}
+
+//判断回文数
+bool isHWS(int num) {
+    int t = num, ans = 0;
+    while (t) {
+        ans = ans * 10 + t % 10;
+        t /= 10;
+    }
+    return ans == num;
+}
+
+int main() {
+    //AC
+    int a, b;
+    cin >> a >> b;
+    if (b >= 1e7)b = 1e7;
+    get_primes(b);
+    for (int i = 0; i < cnt; i++)
+        if (primes[i] >= a && isHWS(primes[i]))
+            printf("%d\n", primes[i]);
+    return 0;
+}