/* Input - Upper Limit for Pair Searching. (Uses 100 by default) Output - Prime Pairs that satisfy the Challenge Condition. Lines - 32 (Excluding Docstrings). Created By - Kinshuk Vasisht (on 05/02/2018) */ #include #include #include /// bool Singlr(int); /// -> Checks if number is a single digit. bool Singlr(int n) { return n%10==n; } /// int DgtSum(int); /// -> Return Sum of Digits of n recursively. int DgtSum(int n) {if(n==0) return 0; return n%10+DgtSum(n/10);} /// bool Prime(int); /// -> Checks if n is Prime bool Prime(int n) { if(n==1) return false; else if(n==2||n==3) return true; for(int i=2;i<=std::sqrt(n);i++) if(n%i==0) return false; return true; } /// bool Condtn(int,int); /// -> Checks if a, b satisfy the condition. bool Condtn(int a, int b) { if(not Prime(a) or not Prime(b)) return 0; int ps = a*b; while(not Singlr(ps)) { if(ps==a or ps==b) return 1; ps=DgtSum(ps); } if(ps==a or ps==b) return true; return false; } int main() { int mr=100,a,b,k=1; std::cin>>mr; if(std::cin.fail()||std::cin.bad()) mr=100; /// Default Case. int x = (mr<=100)?2:((mr<=1000)?3:4); for(int i=2;i<=mr;i++) for(int j=i+1;j<=mr;j++) if(Condtn(i,j)) { std::cout<

Challenge - Prime Pairs