Generate the sum probability distribution of several random numbers

Baidu intern recruitment pen questions:
 

 
Compile the function Foo (int x, int y, int N)
 

 
Calculation: X integers with the size of [1, y] are randomly generated. What is the sum of them and the probability of n?
 

 
Solution: use an array count [m] [k] to generate a random number for a total of m times, and calculate the number of times for K. initialize count [1] [1], count [1] [2] .. count [1] [Y] = 1
 

 
Random Number generated for the I time: the probability (or number of times) for the sum of I * min to I * Max needs to be changed (min = 1, max = y)
 

 
Count [I] [J] = count [I-1] [J-1] + Count [I-1] [J-2] .. count [I-1] [J-y + 1]
 

 
The two-dimensional array can be used with two one-dimensional arrays.
 

 // Foo. cpp: defines the entry point for the console application.  // # Include" Stdafx. h "# Include <iostream> # include <math. h> using namespace STD; Double Foo ( Int X,Int Y, Int N ){ If (N> X * Y | n <X) Return 0; Double T = POW (( Double ) Y, X ); If (N = x | n = x * Y) Return 1/T; If (X = 1) Return ( Double ) 1/y; Int Flag = 1;Double * P [2]; P [0] = New   Double [X * Y + 1]; P [1] = New   Double [X * Y + 1]; Int I; For (I = 1; I <= x * Y; I ++) {P [0] [I] = 0; P [1] [I] = 0 ;} For (I = 1; I <= y; I ++) {P [0] [I] = 1 ;} For (I = 2; I <= x; I ++ ){ For ( Int J = I; j <= I * Y; j ++) {P [flag] [J] = 0; For ( Int K = 1; k <= Y & J-k> 0; k ++) P [flag] [J] + = P [1-Flag] [J-K];} flag = 1-flag ;} // For (I = x; I <= x * Y; I ++)  // Printf ("% 2D: % F \ n", I, P [1-Flag] [I]);  Double Ret = P [1-Flag] [N]/t; Delete [] P [0]; Delete [] P [1]; Return RET ;} Int Main ( Int Argc, Char * Argv []) {printf (" % F \ n ", Foo (9, 6, 23 )); Return 0 ;}

Reference: http://zhedahht.blog.163.com/blog/static/254111742009101524946359/

 

 

2. design function. The input is a string containing Chinese characters, English letters, numbers, and other characters. It is encoded as GBK. The encoding rules for Chinese characters are assumed to be dual-byte. The height is greater than 0x80, and the low byte is arbitrary.

A) Write a function in a common language (C/C ++/PHP/Java). The function is to extract Chinese characters from the input text in order to form a new text string and return it to the caller.

B) if the caller sometimes wants to get the full Chinese content of the input string and sometimes the English content, how should the function be designed.

C) if the caller wants to obtain one or more of the three types of Characters in the input string that contain Chinese, English, and numbers, how should the function be designed.

Getchar (S, letter | digit | Chinese)

 Enum Type {Chinese = 1, letter = 2, digit = 4 }; Static Inline bool isletter ( Char C ){ Return C> = 'A' & C <= 'Z' | C> = 'A' & C <= 'Z';} string getchar (Const   Char * STR, Int Type = Chinese ){ Int Length = strlen (STR ); Char * TMP = ( Char *) Malloc (Length + 1 )* Sizeof ( Char ); String ret; Int K = 0; For ( Int I = 0; I <length; I ++ ){ If (Type> 0 & 1 ){ If (( Unsigned   Char ) STR [I]> 0x80) {TMP [k ++] = STR [I]; TMP [k ++] = STR [++ I]; Continue ;}} If (Type> 1 & 1) & isletter (STR [I]) {TMP [k ++] = STR [I]; Continue ;} If (Type> 2 & 1) & isdigit (STR [I]) {TMP [k ++] = STR [I]; Continue ;} TMP [k] = '\ 0'; ret. Assign (TMP ); Free (TMP ); Return RET ;}