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Introduction The Two Sum problem is a popular coding interview question where we must find two indices of an array whose values add up to a given target. This program demonstrates a simple brute-force solution in C using nested loops and dynamic memory allocation. Problem Statement Given an integer array and a target value, return the indices of the two numbers such that they add up to the target. Each input has exactly one solution, and the same element cannot be used twice. The result should return the indices, not the values. If no solution exists, return NULL. Algorithm / Logic Explanation Start the program. Traverse the array using a loop from index 0 to numsSize - 1 . Inside this loop, use another loop starting from i + 1 to numsSize - 1 . For every pair (i, j) , check if nums[i] + nums[j] == target . If condition becomes true: Allocate memory for 2 integers using malloc() . Store indices i and j . Set returnSize = 2 . Return the result poi...
How to Check Palindrome String in C Programming (With Example)
Intro
A palindrome string is a string that reads the same forwards and backwards. In this post, we will learn how to check whether a given string is a palindrome using a simple C program. This example is beginner-friendly and helps in understanding string handling and logical thinking in C programming.
Problem Statement
The program takes a string as input from the user. The input string may contain characters and spaces. The task is to check whether the given string is a palindrome or not. If the string reads the same from left to right and from right to left, the program should display that it is a palindrome; otherwise, it should display that it is not a palindrome. This problem helps beginners practice string manipulation and conditional logic in C programming.
Algorithm / Logic Explanation
To check whether a string is a palindrome, we use the two pointer technique, which is simple and efficient. First, the program takes a string input from the user. Two integer variables are used as pointers: left and right. The left pointer is initialized at the beginning of the string, while the right pointer is initialized at the end of the string using the length of the string.
The program compares the characters at the left and right positions. If both characters are the same, it means the string is matching from both ends. Then, the left pointer moves one step forward and the right pointer moves one step backward. This process continues until the two pointers meet in the middle of the string.
If at any point the characters do not match, the program immediately concludes that the string is not a palindrome. If all character comparisons are successful, the string is confirmed as a palindrome. This method works because palindrome strings have symmetrical characters around their center.
C Program to Check Palindrome String
#include<stdio.h>
#include<string.h>
void pal(char str[])
{
int left = 0, right = strlen(str) - 1;
while (left < right)
{
if (str[left] != str[right])
{
printf("No, Entered string is not palindrome:\n");
return;
}
left++;
right--;
}
printf("Yes, Entered string is palindrome:\n");
}
int main()
{
char str[100];
printf("Enter the string:\n");
scanf(" %[^\n]", str);
pal(str);
}
Sample Input / Output
Example 1
Input
madam
Output
Yes, Entered string is palindrome
Example 2
Input
hello
Output
No, Entered string is not palindrome
Edge Cases / Notes
An empty string or a single character is always considered a palindrome.
The program is case-sensitive, so uppercase and lowercase letters are treated as different characters.
Spaces and special characters are compared as they are entered.
This program is designed for learning purposes and works best with simple text inputs.
Conclusion
In this post, we learned how to check whether a string is a palindrome using a simple C program. By applying the two pointer technique, we efficiently compared characters from both ends of the string. This logic is easy to understand and is widely used in beginner-level string problems.
FAQs
Q1: What is a palindrome string?
A palindrome string is a string that reads the same from left to right and from right to left. Examples include words like “madam”, “level”, and “radar”.
Q2: Why is the two pointer method used in this program?
The two pointer method helps compare characters from both ends of the string at the same time. This reduces unnecessary comparisons and makes the logic simple and efficient.
Q3: Does this program work with spaces in the string?
Yes, this program allows spaces in the input string and compares them as regular characters.
Q4: Is this program case-sensitive?
Yes, uppercase and lowercase letters are treated as different characters in this program.
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