Count the number of various characters in the string

                                                 Count the number of various characters in the string

One 、 Title Description

　　 Enter a line of string from the keyboard , Count the capital letters 、 Lowercase letters 、 Space 、 Numbers 、 And the number of other characters .( More , Please see the Programmers are on the road )

Two 、 Analysis answers

　　 This paper mainly studies C Relevant knowledge points of language string . String processing is C A very important knowledge point in language , But in C Language summary has no string type , therefore , Strings can only be used in the form of character arrays or character pointers . Remember a little , Whether we use string constants or string variables , For the convenience of processing strings , System Automatically   Add an end flag to the string ’\0’（’\0’ representative ASCII by 0 The characters of , It is not a displayable character , Just an empty operator , Provide sign recognition function , Using it as an end sign will not produce additional operations or add valid characters ）. Strings are stored continuously in memory , Occupy a continuous space .
　　 The code is as follows ：

#include<stdio.h>
#include<stdlib.h>

int main(){

	int n,i=0,alpha=0,Alpha=0,digit=0,space=0,other=0;

	char *str;

   // Input N, Determine the length of the string ; Then apply for the address space of corresponding length and assign it to str.
	scanf("%d",&n);
	//    elimination scanf function   Left over line breaks   Interference with statistics 
	getchar();

	if((str = (char *)malloc(n * sizeof(char))) == NULL){
	
		printf("Not able to allocate memory");
		exit(1);
	}

   // Input string . Pay attention here , Selection of character input function ,scanf Because spaces are not acceptable , It will lead to the inaccuracy of the final statistical results , Therefore, it is selected here gets()/getchar();

	gets(str);

	// Count the number of characters .  String to '\0' Continuously stored in memory for terminators ,
	while(*(str+i) != '\0'){
	
			if(*(str+i) >= 'A' && *(str+i) <= 'Z' ) {  // Big and small letters 
				 Alpha ++;
			}else if(  *(str+i) >= 'a' && *(str+i) <= 'z'  ){  // Lowercase letters 
				 alpha ++;
			}else if( *(str+i) >= '0' && *(str+i) <= '9' ){   //  Numbers 
				  digit ++;
			}else if( *(str+i) == ' ' ){   // Space 
				  space ++;
			}else{  // Other characters 
				other ++;
			}

			i++;
	}
	printf("alpha = %d \n  Alpha = %d\n  digit = %d \n  space=%d\n other=%d \n ",alpha,Alpha,digit,space,other);

	return 0;

}

　　 You can also use the following methods ：

#include<stdio.h>
#include<stdlib.h>

int main(){

	int n,i=0,alpha=0,Alpha=0,digit=0,space=0,other=0;

	char *str;

   // Input N, Determine the length of the string ; Then apply for the address space of corresponding length and assign it to str.
	scanf("%d",&n);
	//    elimination scanf function   Left over line breaks   Interference with statistics 
	getchar();

	if((str = (char *)malloc(n * sizeof(char))) == NULL){
	
		printf("Not able to allocate memory");
		exit(1);
	}

   // Input string . Pay attention here , Selection of character input function ,scanf Because spaces are not acceptable , It will lead to the inaccuracy of the final statistical results , Therefore, it is selected here gets()/getchar();
	
	// You can also enter a string in this way 
		while(i<=n){
	
		*(str+i) = getchar();

		i++;
	}
	
	//   You can also cycle through the string according to the number of characters you enter 

	  	for(i=0;i<n;i++){
	
				if(*(str+i) >= 'A' && *(str+i) <= 'Z' ) {  // Big and small letters 
					 Alpha ++;
				}else if(  *(str+i) >= 'a' && *(str+i) <= 'z'  ){  // Lowercase letters 
					 alpha ++;
				}else if( *(str+i) >= '0' && *(str+i) <= '9' ){   //  Numbers 
					  digit ++;
				}else if( *(str+i) == ' ' ){   // Space 
					  space ++;
				}else{  // Other characters 
					other ++;
				}
	   }
	
	

	printf("alpha = %d \n  Alpha = %d\n  digit = %d \n  space=%d\n other=%d \n ",alpha,Alpha,digit,space,other);

	return 0;

}

3、 ... and 、 Sum up

　　1, String processing is often encountered in computers , therefore , Understand the definition of string 、 initialization 、 Input and output 、 Storage mode is very important .
　　2,C The language compilation system will automatically add ’\0’ Identifier as a sign of the end of the string , therefore , This flag can be used to judge whether the loop jumps out when reading the characters in the string in a loop .
　　3, In order to facilitate the input and output of strings ,C The language provides the exception scanf() In addition to the getchar()、gets() function . It is convenient for us to output strings .　
　　4, The array name of the character array is the first address of the string , Is a constant , It cannot be calculated , A string pointer is a pointer variable , It can be calculated , Therefore, you can operate strings more flexibly , Improve string processing efficiency .
　　( If there are any questions , You can comment below , thank you )