Print string of odd length in 'X' format in C Program.

Given a string of odd length, we need to print it in 'X' format where characters are displayed diagonally from top-left to bottom-right and top-right to bottom-left, creating an X pattern.

Syntax

void printXPattern(char str[], int len);

Algorithm

1. Use variable i to iterate through rows (0 to len-1)
2. Calculate j = len-1-i for the right diagonal position
3. For each column position k, print character if k == i or k == j, otherwise print space
4. Move to next line after each row

Example

Here's the C implementation to print a string in X format −

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

void printXPattern(char str[], int len) {
    for (int i = 0; i < len; i++) {
        int j = len - 1 - i;
        for (int k = 0; k < len; k++) {
            if (k == i || k == j)
                printf("%c", str[k]);
            else
                printf(" ");
        }
        printf("
");
    }
}

int main() {
    char str[] = "tutorialpoint";
    int len = strlen(str);
    
    printf("String in X format:
");
    printXPattern(str, len);
    
    return 0;
}

String in X format:
t           t
 u         n 
  t       i  
   o     a   
    r   l    
     i p     
      a      
     l o     
    p   i    
   o     n   
  i       t  
 n         t 
t           u

How It Works

• Left diagonal: Position i gives us characters from top-left to bottom-right
• Right diagonal: Position j = len-1-i gives us characters from top-right to bottom-left
• Space filling: All other positions are filled with spaces to maintain the X structure
• Center intersection: For odd-length strings, the center character appears at the intersection of both diagonals

Key Points

• This algorithm works best with odd-length strings to create a symmetric X pattern
• Time complexity is O(n²) where n is the string length
• Space complexity is O(1) as no extra space is used

Conclusion

The X pattern printing technique uses two diagonal traversals to create an intersection pattern. This approach effectively demonstrates nested loops and conditional character placement in C programming.