Find the number of stair steps | Modified Binary search function to solve the equation ; if mid is solution to equation ; if our solution to equation lies between mid and mid - 1 ; if solution to equation is greater than mid ; if solution to equation is less than mid ; Driver Code ; call binary search method to solve for limits 1 to T ; Because our pattern starts from 2 , 3 , 4 , 5. . . so , we subtract 1 from ans
< ? php function solve ( $ low , $ high , $ T ) { while ( $ low <= $ high ) { $ mid = ( $ low + $ high ) / 2 ; if ( ( $ mid * ( $ mid + 1 ) ) == $ T ) return $ mid ; if ( $ mid > 0 && ( $ mid * ( $ mid + 1 ) ) > $ T && ( $ mid * ( $ mid - 1 ) ) <= $ T ) return $ mid - 1 ; if ( ( $ mid * ( $ mid + 1 ) ) > $ T ) $ high = $ mid - 1 ; else $ low = $ mid + 1 ; } return -1 ; } $ T = 15 ; $ ans = solve ( 1 , $ T , 2 * $ T ) ; if ( $ ans != -1 ) $ ans -- ; echo " Number ▁ of ▁ stair ▁ steps ▁ = ▁ " , $ ans , " STRNEWLINE " ; ? >