Data-course 1st-door to advanced masters

Lesson 1st-the door to advanced masters

 

1. Understanding the nature of a program

Programs exist for actual problems. Essentially, programs are steps to solve the problem.

Problem:

How to put elephants in the refrigerator?

(1) open the refrigerator door (2) Put the elephant in (3) Close the refrigerator door

Elephan * E = getelep ();

Int F = open ("fridge ");

Put (F, E );

Close (F

 

1. First understand the actual problem

(1) confirm the problem type.

For example, calculate the number of minimum values.

(2) confirm the solution steps.

For example, open a file, read data, close a file, computation, and.

 

Let's look at a program that calculates the sum of the First n items:

# Include <stdio. h>

# Include <malloc. h>

Long sum1 (int n)

{

Long ret = 0;

Int * array = (int *) malloc (N * sizeof (INT ));

Int I = 0;

For (I = 0; I <n; I ++)

{

Array [I] = I + 1;

}

For (I = 0; I <n; I ++)

{

RET + = array [I];

}

Free (array );

Return ret;

}

Long sum2 (int n)

{

Long ret = 0;

Int I = 0;

For (I = 1; I <= N; I ++)

{

RET + = I;

}

Return ret;

}

Long sum3 (int n)

{

Long ret = 0;

If (n> 0)

{

Ret = (1 + n) * n/2;

}

Return ret;

}

Int main ()

{

Printf ("% d \ n", sum1 (100); // 5050

Printf ("% d \ n", sum2 (100); // 5050

Printf ("% d \ n", sum3 (100); // 5050

Return 0;

}

 

1. Program Evaluation

(1) use up a small amount of memory space to solve the problem

(2) step-by-step solution

Excellent developers need to pursue the high "cost-effectiveness" of code "!

 

Summary:

(1) The program is stored for specific problems.

(2) The program should solve the problem.

(3) The same problem can be solved in many ways.

 

 

 

 

 

 

 

 

 

 

 

 

Data-course 1st-door to advanced masters