Sandglass Pattern
Hard
C
Pattern Printing
38 views
Problem Statement
* * * * *
* * * *
* * *
* *
*
* *
* * *
* * * *
* * * * *
Inverted triangle above, normal below. Mirror image vertically.
Input Format
No input required.
Fixed number of rows.
Fixed number of rows.
Output Format
Star pattern with:
• Inverted triangle on top
• Normal triangle at bottom
• Vertically mirrored
• Inverted triangle on top
• Normal triangle at bottom
• Vertically mirrored
Constraints
• Fixed rows (e.g. 5 up + 4 down)
• Nested loops only
• Nested loops only
Concept Explanation
The pattern is divided into two parts:
upper inverted triangle and lower normal triangle.
upper inverted triangle and lower normal triangle.
Step-by-Step Explanation
Upper Inverted Triangle
1.Use an outer loop for rows from 0 to n-1.
2.For each row i:
3.Print i leading spaces.
4.Print (n - i) stars with space after each star.
5.Move to the next line.
Lower Normal Triangle
1.Use another outer loop for rows from n-2 down to 0.
2.For each row i:
3.Print i leading spaces.
4.Print (n - i) stars with space after each star.
5.Move to the next line.
1.Use an outer loop for rows from 0 to n-1.
2.For each row i:
3.Print i leading spaces.
4.Print (n - i) stars with space after each star.
5.Move to the next line.
Lower Normal Triangle
1.Use another outer loop for rows from n-2 down to 0.
2.For each row i:
3.Print i leading spaces.
4.Print (n - i) stars with space after each star.
5.Move to the next line.
Concept Explanation
The pattern is divided into two parts:
upper inverted triangle and lower normal triangle.
upper inverted triangle and lower normal triangle.
Step-by-Step Explanation
Upper Inverted Triangle
1.Use an outer loop for rows from 0 to n-1.
2.For each row i:
3.Print i leading spaces.
4.Print (n - i) stars with space after each star.
5.Move to the next line.
Lower Normal Triangle
1.Use another outer loop for rows from n-2 down to 0.
2.For each row i:
3.Print i leading spaces.
4.Print (n - i) stars with space after each star.
5.Move to the next line.
1.Use an outer loop for rows from 0 to n-1.
2.For each row i:
3.Print i leading spaces.
4.Print (n - i) stars with space after each star.
5.Move to the next line.
Lower Normal Triangle
1.Use another outer loop for rows from n-2 down to 0.
2.For each row i:
3.Print i leading spaces.
4.Print (n - i) stars with space after each star.
5.Move to the next line.
Input / Output Format
Input Format
No input required.
Fixed number of rows.
Fixed number of rows.
Output Format
Star pattern with:
• Inverted triangle on top
• Normal triangle at bottom
• Vertically mirrored
• Inverted triangle on top
• Normal triangle at bottom
• Vertically mirrored
Constraints
• Fixed rows (e.g. 5 up + 4 down)
• Nested loops only
• Nested loops only
Examples
Input:
Output:
* * * * *
* * * *
* * *
* *
*
* *
* * *
* * * *
* * * * *
Example Solution (Public)
#include <stdio.h>
int main() {
int n = 5; // height of triangle
int i, j;
for (i = 0; i < 2*n - 1; i++) {
int spaces = (i < n) ? i : (2*n - 2 - i);
int stars = n - spaces;
// leading spaces
for (j = 0; j < spaces; j++)
printf(" ");
// stars
for (j = 0; j < stars; j++)
printf("* ");
printf("n");
}
return 0;
}
Official Solution Code
#include <stdio.h>
int main() {
int n = 5; // height of triangle
int i, j;
for (i = 0; i < 2*n - 1; i++) {
int spaces = (i < n) ? i : (2*n - 2 - i);
int stars = n - spaces;
// leading spaces
for (j = 0; j < spaces; j++)
printf(" ");
// stars
for (j = 0; j < stars; j++)
printf("* ");
printf("n");
}
return 0;
}
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