33 lines
731 B
C++
33 lines
731 B
C++
#include<bits/stdc++.h>
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using namespace std;
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const int N = 1e8 + 10;
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int primes[N], cnt;
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bool st[N];
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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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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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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 = a; i <= b; i++)
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if (!st[i] && isHWS(i))
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cout << i << endl;
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return 0;
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} |