One dimensional array exercise

One 、 exercises

1. Before the n Put the number behind

Ideas ：

The array length is len
First, reverse the entire array
Then on the front len - n The number is in reverse order , This will be behind n To len Put the number to the front
To the back again n Elements are in reverse order , In this way, the former n The number is put behind

The time complexity is O(n)

Code ：

void Reverse(int* arr, int begin, int end)// Yes  begin  To  end  Data in reverse order 
{
    
	assert(arr != NULL && begin <= end);
	int temp = 0;
	int len = (end - begin + 1) / 2;
	for(int i = 0;i<len;i++,begin++,end--) 
	{
       
		temp = arr[begin];
		arr[begin] = arr[end];
		arr[end] = temp;
	}
}


void Adjust(int* arr, int len, int m) 
{
    
	assert(arr != NULL);
	Reverse(arr, 0, len-1);// Yes arr The whole is in reverse order 
	Reverse(arr, 0, len - 1 - m);// To the front len-m Elements in reverse order 
	Reverse(arr, len - m, len - 1);// Right back m Elements in reverse order 
}

test ：

int main()
{
    
    int arr[] = {
     1,2,3,4,5,6,7 };
	int len = sizeof(arr) / sizeof(arr[0]);
	Adjust(arr, len, 4);
	for (int i = 0; i < len; i++) 
	{
    
		printf("%-2d", arr[i]);
	}
return 0;
}

Running results ：

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2. Replace string characters

Code ：

int GetCharCount(char *ch,char c) // Count the number of characters to be replaced 
{
    
	int count = 0;int i = 0;
	assert(ch!=NULL);
	while (ch[i] != '\0') 
	{
    		
		if (ch[i] == c)count++;
		i++;
	}
	return count;
}


void Rplace(char* ch, char aim, int num, char newc) // Replace character 
{
    
	assert(ch!=NULL);
	int count = GetCharCount(ch,aim);
	int i = strlen(ch), j = i + count * (num - 1);
	while (i != j) 
	{
    
		if (ch[i] != aim) 
		{
    
			ch[j--] = ch[i--];
		}
		else 
		{
    
			for (int a = 0; a < num; a++) 
			{
    
				ch[j--] = newc;
			}
			i--;
		}
	}
}

test ：

int main()
{
    
    char ch[100] = "I am a student";
	Rplace(ch, ' ', 4, '!');
	for (int i = 0; i < strlen(ch); i++) 
	{
    
		printf("%c",ch[i]);
	}
	return 0;
}

Running results ：

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3. Realization strcpy()

Code ：

void my_strcpy(char* arr,char* brr) 
{
    
	assert(arr != NULL && brr != NULL);
	int size = strlen(brr)+1,i=0;
	while(i<=size)
	{
    
		arr[i] = brr[i];
		i++;
	}
}

test ：

int main()
{
    
    char ch1[100] = "hi hello";
	char ch2[] = "world";
	my_strcpy(ch1, ch2);
	for (int i = 0; i < strlen(ch1); i++)
	{
    
		printf("%c", ch1[i]);
	}
    return 0;
}

Running results ：

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4. Realization strcat()

Code ：

void my_strcat(char* arr, char* brr)
{
    
	assert(arr!=NULL && brr!=NULL);
	int i = strlen(arr), j = 0;
	while (arr[j] != '\0') 
	{
    
		arr[i] = brr[j];
		i++;
		j++;
	}
}

test ：

int main()
{
      
    char ch1[100] = "hello ";
	char ch2[] = "world";
	my_strcat(ch1, ch2);
	for (int i = 0; i < strlen(ch1); i++)
	{
    
		printf("%c", ch1[i]);
	}
	return 0;
}

Running results ：

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Two 、 Assertion assert() Use

Add header file when using ：#include<assert.h>

Using the logical ：
assert( Judge the condition );

Can be seen as ：
if（ Judge the condition ）
{
Condition if true , Continue to execute the statement ;
}
else Jump out of

If the result of the judgment condition is 1, Continue operation
If 0, Then the program crashes

Code ：

void test(int a,int b) 
{
    
	assert(a==b);
	printf(" equal \n\n");
}

When a 、b Wait a moment ：

int main()
{
    
    int a = 1, b = 2 ;	
	test(a,b);
	return 0;
}

Running results ：
Because the result of the judgment condition is 0, The program crash

When a 、b When equal ：

int main()
{
    
    int a = 1, b = 1 ;	
	test(a,b);
	return 0;
}

Running results ：