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Description:
Count the number of prime numbers less than a non-negative number, n.
传送门：https://leetcode.com/problems/count-primes/
尽可能把查找次数缩小，直接用双重for会超时。
public class Solution { public int countPrimes(int n) { //默认全为false boolean res[] = new boolean[n]; for(int i = 2; i * i < n; i++) { if(!res[i]){ //直接找到相乘小与n的数，说明不是素数 for(int j = i; i * j < n; j++){ res[i * j] = true; } } } int count = 0; for(int i = 2; i < n; i++) if(res[i] == false) count++; return count; } }
Leetcode-204(Java) Count Primes
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原文地址：http://www.cnblogs.com/zetrov/p/4703909.html
