c_cpp C程序读取字符串并检查它是否是回文，而不使用库函数。显示结果。

Posted 2021-05-14

/*
* C Program to Check whether a given String is Palindrome or not
* using Recursion
*/

#include <stdio.h>
#include <string.h>

void check(char[], int);

int main() {

	char string[25];

	printf("enter a string:\n");
	scanf("%s", string);

	check(string, 0);

	return 0;
}

void check(char word[], int index) {

	int len = strlen(word) - (index + 1);

	if (word[index] == word[len]) {
		if (index + 1 == len || index == len) {
			printf("The entered word is a palindrome.\n");
			return;
		}

		check(word, index + 1);
	}

	else {
		printf("The entered word is not a palindrome.");
	}
}

/*
* C program to read a string and check if it's a palindrome, without
* using library functions. Display the result.
*/
#include <stdio.h>
#include <string.h>

int main() {

	char string[25],
		reverse_string[25] = { '\0' };
	int flag = 0,
		i,
		length = 0;

	fflush(stdin);
	printf("enter string...\n");
	gets_s(string);

	for (i = 0; string[i] != '\0'; i++) {
		length++;
	}

	//hello = 6 | start form 5 | 
	//olleh	


	//reverse the string
	for (i = length - 1; i >= 0; i--) {
		reverse_string[length - i - 1] = string[i];
	}

	for (i = 0; i < length; i++) {
		if (reverse_string[i] == string[i]) {
			flag = 1;
		}
		else {
			flag = 0;
		}
	}


	if (flag == 1) {
		printf("%s is a palindrome\n", string);
	}
	else {
		printf("%s is not a palindrome\n", string);
	}
	

	return 0;
}

/*
* C Program to Check whether a given String is Palindrome or not
* using Recursion
*/

#include <stdio.h>
#include <string.h>

void check(char[], int);

int main() {

	char string[25];

	printf("enter a string:\n");
	scanf("%s", string);

	check(string, 0);

	return 0;
}

void check(char word[], int index) {

	int len = strlen(word) - (index + 1);

	if (word[index] == word[len]) {
		if (index + 1 == len || index == len) {
			printf("The entered word is a palindrome.\n");
			return;
		}

		check(word, index + 1);
	}

	else {
		printf("The entered word is not a palindrome.");
	}
}