Find the smallest number X such that X ! contains at least Y trailing zeros . | Function to count the number of factors P in X ! ; Function to find the smallest X such that X ! contains Y trailing zeros ; Driver code
< ? php function countFactor ( $ P , $ X ) { if ( $ X < $ P ) return 0 ; return ( ( int ) ( $ X / $ P ) + countFactor ( $ P , ( $ X / $ P ) ) ) ; } function findSmallestX ( $ Y ) { $ low = 0 ; $ high = 5 * $ Y ; $ N = 0 ; while ( $ low <= $ high ) { $ mid = ( int ) ( ( $ high + $ low ) / 2 ) ; if ( countFactor ( 5 , $ mid ) < $ Y ) { $ low = $ mid + 1 ; } else { $ N = $ mid ; $ high = $ mid - 1 ; } } return $ N ; } $ Y = 10 ; echo ( findSmallestX ( $ Y ) ) ; ? >