C language introduction practice (11): enter a group of positive integers and sum the numbers in reverse order

This is a 《C Language introduction practice 》 Series No 11 piece .
Last one ：C Language introduction practice (10)： Mold taking problem

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subject

Any set of positive integers entered on the keyboard （ Any number ）, Find the sum of all numbers in reverse order , The number in reverse order here refers to the number read from right to left , for example 123 The number in reverse order is 321,1200 The number in reverse order is 21. End the program when entering a non number . Please program to solve this problem .

requirement

Example of input / output format 1：

Input ：170< enter >
x< enter >
Output ：71

Example of input / output format 2：

Input ：21< enter >
130< enter >
89< enter >
125< enter >
90< enter >
a< enter >
Output ：671

Reference code

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

//  Define a function , Calculate input integer n In reverse order  
int reverseNum(int n) {
    
	int a = 0;
	while(n>0) {
    
		a = a*10 + n%10;
		n /= 10;// namely n=n/10
	}
	return a;
}
int main(int argc, char *argv[]) {
    
	int result = 0;
	int n;
	char ch;
	int flag = 1;
	while(flag) {
    
		n = 0;
		ch = getchar();
		while(ch!='\n' && ch!=EOF) {
    
			if (ch>='0' && ch <='9') {
    
				n = n*10 + ch-'0';
			} else {
    
                // Read characters that are not positive integers , Set exit flag 
				flag = 0;
				break;
			}
			ch = getchar();
		} 
        // Corresponding to the legal positive integer value in the input group , Get its inverse ordinal number , Add to the answer 
		result += reverseNum(n);
	}
	printf("%d", result);
	return 0;
}

Code duplicate

We define a function （ Functions are used to encapsulate reusable code units ）,int reverseNum(int n), According to the entered integer value n Calculation return n In reverse order .

&& yes Logic and Symbol , yes “ also ” It means .

getchar() In the standard library header file stdio.h In a statement , Used to input from standard （ It's usually a keyboard ） Read a character .

EOF yes stdio.h Constants defined in （ Constant value is -1）, Indicates that you have read the file / End of standard input . Because normally , Read a byte from a file or standard input , This byte must be >=0 The characters of , So it can be stipulated -1 Constant expression reading is over .