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39 lines
881 B
39 lines
881 B
#include<bits/stdc++.h>
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using namespace std;
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const int N = 100000010;
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//欧拉筛
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int primes[N], cnt; // primes[]存储所有素数
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bool st[N]; // st[x]存储x是否被筛掉
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void get_primes(int n) {
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for (int i = 2; i <= n; i++) {
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if (!st[i]) primes[cnt++] = i;
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for (int j = 0; primes[j] <= n / i; j++) {
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st[primes[j] * i] = true;
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if (i % primes[j] == 0) break;
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}
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}
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}
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//判断回文数
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bool isHWS(int num) {
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int t = num, ans = 0;
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while (t) {
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ans = ans * 10 + t % 10;
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t /= 10;
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}
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return ans == num;
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}
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int main() {
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//AC
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int a, b;
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cin >> a >> b;
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if (b >= 1e7)b = 1e7;
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get_primes(b);
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for (int i = 0; i < cnt; i++)
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if (primes[i] >= a && isHWS(primes[i]))
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printf("%d\n", primes[i]);
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return 0;
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} |