【HDU2136】 Largest prime factor
2017-08-09 12:54
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Everybody knows any number can be combined by the prime number.
Now, your task is telling me what position of the largest prime factor.
The position of prime 2 is 1, prime 3 is 2, and prime 5 is 3, etc.
Specially, LPF(1) = 0.
InputEach line will contain one integer n(0 < n < 1000000).
OutputOutput the LPF(n).
Sample Input
Sample Output
Now, your task is telling me what position of the largest prime factor.
The position of prime 2 is 1, prime 3 is 2, and prime 5 is 3, etc.
Specially, LPF(1) = 0.
InputEach line will contain one integer n(0 < n < 1000000).
OutputOutput the LPF(n).
Sample Input
1 2 3 4 5
Sample Output
0 1 2 1 3
/** 素数筛法,每遍历一个外层点时 将它的所有倍数全部赋值为num(当前质因子的序号) 从小到大逐个遍历 4000 即为最大质因子的序号 */ #include<iostream> #include<algorithm> #include<cstring> #include<cmath> #include<cstdio> #include<queue> #include<vector> using namespace std; const int Max = 1e6 + 5; int n; int a[Max]; int main() { memset(a, 0, sizeof(a)); int num = 1; //质因子序号 for(int i = 2; i <= Max; i++) { if(!a[i]) { for(int j = i; j <= Max; j += i) //i的所有倍数都被赋值为同一个序号 { a[j] = num; } num++; } } while(scanf("%d", &n) != EOF) { printf("%d\n", a ); } return 0; }
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