if character from both String is not same then we take the minimum from three specified operation
else { DP [ i % 2 , j ] = 1 + Math . Min ( DP [ ( i - 1 ) % 2 , j ] , Math . Min ( DP [ i % 2 , j - 1 ] , DP [ ( i - 1 ) % 2 , j - 1 ] ) ) ; } } }