ATOI super resolution

Function description ：

The library has its own functions , A reference header file is required #include<stdlib.h>

The string 123 Convert to integer number 123（ one hundred and twenty-three ）

characteristic ：

1. Input 123 Output ->123 // Direct conversion
2. Input 123.5 Output ->123 //int Type conversion （ It can also be understood as directly putting . Treat as character ）
3. Input -123 Output ->-123 // Characters to be recognized ‘-’, convert to -（ Minus sign ）
4. Input +123 Output ->123
5. Input   （ Space ）123 Output ->123 // If there are spaces , Move forward directly to cover the space
6. Input 12  （ Space ）3 Output ->12 // If there is a space after it, it has stopped , Unable to continue to identify
7. Input -+123 Output ->0 // For two or more +- The symbol does not recognize
8. Input --123 Output ->0
9. Input 123abcd123 Output ->123
10. Input 123--++123 Output ->123

thought （ Distributed solution ）：

1, Input 123 Output ->123

1, Get the number of characters and the number of digits corresponding to a single character converted to a number

The relationship between the number of characters and the number of digits ：1234  -4 Characters -4 It's a thousand 10 Of 3 Power

How to get the number of characters ： The judgment character is in ’0’,’9’ Between , Definition count Add up and

The number of digits in a number is 10 Of count-1 Power

2, Realize the conversion of single character ：

adopt ASCCI code ‘1’-‘0’=1;

eg: 0：ASCCI 48  1:ASCCI 49

Code implementation ：

int GetBite(char* arr, int length)

{

        int count = 0;

        int len;

        for (int i = 0; i < len; i++)

        {

                if (arr[i] >= '0' && arr[i] <= '9')

                {

                        count++;

                }

        }

        return count;

}

int my_atoi(char* arr, int len)

{

        assert(arr != NULL);

        int result = 0;

        int bite = GetBite(arr, len);

        for (int i = 0; i < len; i++)

        {

                result = (arr[i] - '0') * pow(10, bite - 1); // Code interpretation ①

        }

        return result;

}

①result=(arr[i]-'0')*pow(10,bite-1);

pow(10,bite-1): pow The function is to implement 10 Of bite-1 Power

arr[i]-'0'： Convert characters to numbers

2, Input 123.5 Output ->123 //int Type conversion （ It can also be understood as directly putting . Treat as character ）

Modify the code ：

result = (arr[i] - '0') * pow(10, bite - 1);// Code interpretation ②

②(int)： Type cast ,result by int type ,pow by double type ,int*double=double, A strong turn is needed

3, Input -123 Output ->-123 // Characters to be recognized ‘-’, convert to -（ Minus sign ）

Modify the code ：

int flag = 1;// Store the sign

for (int i = 0; i < len; i++) // Change an integer to a positive or negative number

{

        if (arr[i] == '-')

                flag = -1;

        else // Add else Purpose ： If not else,-'-'-'0' It's not a character , Perform error

                result = (int)(result + (arr[i] - '0') * poe(10, bite - 1));

}

4, Input +123 Output ->123

Modify the code ：

int flag = 1;// Store the sign

for (int i = 0; i < len; i++) // Change an integer to a positive or negative number

{

        if (arr[i] == '-')

                flag = -1;

        else if (str[i] == '+') {

                continue;// End the current cycle , Start a new cycle

        else // Add else Purpose ： If not else,-'-'-'0' It's not a character , Perform error

                result = (int)(result + (arr[i] - '0') * poe(10, bite - 1));

}

5, Input   （ Space ）123 Output ->123 // If there are spaces , Move forward directly to cover the space

Modify the code ：

while (arr[i] == ' ')//(*arr)

        arr[i] = arr[i++];//arr++;

6, Input 12  （ Space ）3 Output ->12 // If there is a space after it, it has stopped , Unable to continue to identify

Modify the code ：

GetBite Within the function ：

for (int i = 0; i < len; i++)

        {

                if (arr[i] >= '0' && arr[i] <= '9')

                {

                        count++;

                }

                else

                        break; // When a space is encountered, it will be returned directly

}

7, Input - +123 Output ->0// For two or more +- The symbol does not recognize

8, Input --123 Output ->0

//（7）（8） Empathy , The code is as follows ：

GetBite Within the function ：

// use num To control +- Number

int num = 0;

for (int i = 0; i < len; i++)

{

        if (arr[i] >= '0' && arr[i] <= '9')

        {

                count++;

                if (num >= 2)// If there are two or more +- The result is 0

                        return 0;

        }

                else if (arr[i] == '+' || arr[i] == '-') // obtain +- The number of

                        num++;

                else

                        break; // When a space is encountered, it will be returned directly

}

9, Input 123abcd123 Output ->123

10, Input 123--++123 Output ->123

// And （6） Empathy

The comprehensive code is as follows ：

#define _CRT_SECURE_NO_WARNINGS //VS The compiler needs

#include<assert.h> // Assertion

#include<stdio.h>

#include<string.h>

#include<stdlib.h> // atoi   itoa

#include<math.h>  //pow function

int GetBite(char* arr, int length)

{

        int count = 0, num = 0;

        int len = strlen(str);

        // Delete the blank space

        for (int i = 0; i < len; i++)

        {

        if (arr[i] >= '0' && arr[i] <= '9')

        {

                count++;

                if (num >= 2)// If there are two or more +- The result is 0

                return 0;

          }

                else if (arr[i] == '+' || arr[i] == '-') // obtain +- The number of

                        num++;

                else

                        break;

        }

        return count;

}

int my_atoi(char* arr, int len)

{

        assert(arr != NULL);

        int result = 0;

        int flag = 1;// Store the sign

        int i = 0;

        while (arr[i] == ' ')//(*arr)

        arr[i] = arr[i++];//arr++;

        int bite = GetBite(arr, len);

        int len = strlen(arr);// Recalculate length

        for (int i = 0; i < len; i++) // Change an integer to a positive or negative number

        {

                if (arr[i] == '-')

                        flag = -1;

                else if (arr[i] == '+')

                        continue;// Ends the current cycle

                else // Add else Purpose ： negative -'0' It's not a character , Perform error

                        result = (int)(result + (arr[i] - '0') * pow(10, bite - 1));

        }

        return result * flag;

}

int main()

{

        char arr[] = "123";

        int length = sizeof(arr) / sizeof(arr[0]);

        printf("%d", my_atoi(arr, length));

        return 0;

}

Please let me know in the comments section if there are any mistakes thank you