From ec035ec7395db153834b8ba96b2ce54b597483b0 Mon Sep 17 00:00:00 2001 From: Paul Jungeblut Date: Wed, 9 Nov 2016 20:39:31 +0100 Subject: Adding Kirchhoffs Theorem. --- math/primeSieve.cpp | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) (limited to 'math') diff --git a/math/primeSieve.cpp b/math/primeSieve.cpp index 37ea12c..656a597 100644 --- a/math/primeSieve.cpp +++ b/math/primeSieve.cpp @@ -1,19 +1,19 @@ // Laufzeit: O(n * log log n) -#define N 100000001 // Bis 10^8 in unter 64MB Speicher. -bitset isPrime; +#define N 100000000 // Bis 10^8 in unter 64MB Speicher. +bitset isNotPrime; inline bool check(int x) { // Diese Methode zum Lookup verwenden. if (x < 2) return false; else if (x == 2) return true; else if (!(x & 1)) return false; - else return !isPrime[x / 2]; + else return !isNotPrime[x / 2]; } -inline int primeSieve(int n) { // Rückgabe: Anzahl der Primzahlen <= n. - int counter = 1; - for (int i = 3; i <= min(N, n); i += 2) { - if (!isPrime[i / 2]) { - for (int j = 3 * i; j <= min(N, n); j+= 2 * i) isPrime[j / 2] = 1; +inline int primeSieve() { // Rückgabe: Anzahl der Primzahlen < N. + int counter = 1; // Die 2, die sonst vergessen würde. + for (int i = 3; i < N; i += 2) { + if (!isNotPrime[i / 2]) { + for (int j = 3 * i; j < N; j+= 2 * i) isNotPrime[j / 2] = 1; counter++; }} return counter; -- cgit v1.2.3