'commit'

TangDou/LuoGuBook/L4_14_4.cpp

@@ -0,0 +1,41 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+const int N = 1e8 + 10;
+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] * i <= n; j++) {
+            st[primes[j] * i] = true;
+            if (i % primes[j] == 0) break;
+        }
+    }
+}
+
+//是不是回文数
+bool isHuiWen(int n) {
+    int i = n;
+    int m = 0;
+    while (i) {
+        m = m * 10 + i % 10;
+        i /= 10;
+    }
+    return m == n;
+}
+
+int main() {
+    int a, b;
+    cin >> a >> b;
+    if (b > 10000000) b = 10000000;
+    get_primes(b);
+    //primes[]  2--->b之间所有的质数
+    for (int i = 0; i < cnt; i++) {
+        if (primes[i] < a)continue;
+        if (isHuiWen(primes[i]))
+            cout << primes[i] << endl;
+    }
+    return 0;
+}