Finding prime numbers

Time:2021-2-17

At the same time as the first emperor, eradose, the first person to measure the circumference of the earth, developed the eradose sieve method

thinking

In the given sequence (2-N) table, all the multiples (not 0, 1, itself) of each element are erased, and all the prime numbers less than n are left

Finding prime numbers

Eradose sieve method

Count the prime numbers within n

func countPrimes(n int) int {
   var cnt int
   mark := make([]bool, n)
   for i:=2;i<n;i++{
       if !mark[i]{
           cnt++
           for j:=i+i;j<n;j+=i{
               mark[j] = true
           }
       }
   }
   return cnt
}

Summary

The sum of four squares is just like this

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