Largest number in [ 2 , 3 , . . n ] which is co | Returns true if i is co - prime with numbers in set [ 2 , 3 , ... m ] ; Running the loop till square root of n to reduce the time complexity from n ; Find the minimum of square root of n and m to run the loop until the smaller one ; Check from 2 to min ( m , sqrt ( n ) ) ; Function to find the largest number less than n which is Co - prime with all numbers from 2 to m ; Iterating from n to m + 1 to find the number ; checking every number for the given conditions ; The first number which satisfy the conditions is the answer ; If there is no number which satisfy the conditions , then print number does not exist . ; Driver Code
< ? php function isValid ( $ i , $ m ) { $ sq_i = sqrt ( $ i ) ; $ sq = min ( $ m , $ sq_i ) ; for ( $ j = 2 ; $ j <= $ sq ; $ j ++ ) if ( $ i % $ j == 0 ) return false ; return true ; } function findLargestNum ( $ n , $ m ) { for ( $ i = $ n ; $ i > $ m ; $ i -- ) { if ( isValid ( $ i , $ m ) ) { echo $ i , " STRNEWLINE " ; return ; } } echo " Number ▁ Doesn ' t ▁ Exists STRNEWLINE " ; } $ n = 16 ; $ m = 3 ; findLargestNum ( $ n , $ m ) ; ? >