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June 10, 2021 13:11
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>> Prime Factorisation | |
>>> Resources: | |
T-1: https://cp-algorithms.com/algebra/factorization.html | |
T-2: https://www.geeksforgeeks.org/prime-factorization-using-sieve-olog-n-multiple-queries/ | |
>>> Implementation:O(N log(log(N))) | |
int n; | |
vector<int> primefactor; | |
if(n%2==0) | |
{ | |
primefactor.push_back(2); | |
while(n%2==0) | |
{ | |
n/=2; | |
} | |
} | |
for(int j=3;j<=sqrt(n);j++) | |
{ | |
if(n%j==0) | |
{ | |
primefactor.push_back(j); | |
while(n%j==0) | |
{ | |
n/=j; | |
} | |
} | |
} | |
if(n>2) | |
{ | |
primefactor.push_back(n); | |
} | |
IMPLEMENTATION-2 : O(N log(N)) Useful in case of Integer Factorisation of N numbers. | |
const int N=10000000; | |
int prime[N]; | |
vector<int> primefact; | |
void precompute() | |
{ | |
for(int i=0;i<N;i++) | |
{ | |
prime[i]=i; | |
} | |
for(int i=2;i<N;i+=2) | |
{ | |
prime[i]=2; | |
} | |
for(int i=3;i<=sqrt(N);i++) | |
{ | |
for(int j=i*i;j<N;j+=i) | |
{ | |
if(prime[j]==j) | |
{ | |
prime[j]=i; | |
} | |
} | |
} | |
} | |
void getprimefact(int n) | |
{ | |
while(n!=1) | |
{ | |
primefact.push_back(prime[n]); | |
n/=prime[n]; | |
} | |
} | |
>>> Problems: | |
Problem-1: https://codeforces.com/problemset/problem/385/C | |
Solution : https://codeforces.com/contest/385/submission/87036620 | |
Problem-2: https://codeforces.com/gym/287655/problem/A | |
Solution : https://codeforces.com/gym/287655/submission/86968972 | |
Problem-3: https://codeforces.com/contest/1228/problem/C | |
Solution : https://codeforces.com/contest/1228/submission/86955216 | |
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