📌 Problem Description

Input a positive integer n and output the digital pyramid in the following format (for n=5 as an example):

    1     121    12321   1234321  123454321     

Requirements:

• The numbers must be arranged symmetrically.

• Loops and conditional statements are allowed.

• Advanced: Implement with the simplest code possible.

Difficulty: ⭐️⭐️ (suitable for learners mastering loops and formatted output).

💡 Basic Implementation (Nested Loop Method)

#include <stdio.h>
void print_pyramid(int n) {    for (int i = 1; i <= n; i++) {        // Print left-side spaces        for (int j = 1; j <= n - i; j++) {            printf("  ");        }        // Print left half (increasing)        for (int j = 1; j <= i; j++) {            printf("%d ", j);        }        // Print right half (decreasing)        for (int j = i-1; j >= 1; j--) {            printf("%d ", j);        }        printf("\n");    }}
int main() {    int n;    printf("Please enter the number of pyramid layers:");    scanf("%d", &n);    print_pyramid(n);    return 0;}

🔥Key Points

• Space Control: Number of left-side spaces per line = <span>n - i</span>

• Number Symmetry: Handled in two parts (left half increasing, right half decreasing)

<span>⚡ Advanced Optimization (Single Loop + Mathematical Calculation)</span>

#include <stdio.h>void print_pyramid_opt(int n) {    for (int i = 1; i <= n; i++) {        // Calculate total characters per line (dynamically control spaces)        printf("%*s", (n - i) * 2, ""); // Left-aligned spaces        for (int j = 1; j < 2*i; j++) {            int num = (j <= i) ? j : 2*i - j;            printf("%d ", num);        }        printf("\n");    }}

Optimization Points:

• Use <span>%*s</span> to dynamically control space width

• Single loop calculates number positions using a mathematical formula (<span>num = j <= i ? j : 2*i - j</span>)

⚡ Minimal Recursive Version (Challenge Code Simplification)

#include <stdio.h>
void pyramid(int i, int n) {    if (i > n) return;    printf("%*s", (n - i)*2, "");    for (int j = 1; j < 2*i; j++)         printf("%d ", (j <= i) ? j : 2*i - j);    printf("\n");    pyramid(i + 1, n);}
int main() {    pyramid(1, 5); // Example: 5-layer pyramid    return 0;}

Highlights:

• Recursion replaces loops, resulting in fewer lines of code

• Maintains clear logic while reducing variables

🤔 Common Error Analysis

Issue	Cause	Solution
Numbers Misaligned	Multi-digit placeholders not handled	Use <span>%2d</span> or <span>%-2d</span> for fixed width
Right Side Not Symmetrical	Incorrect starting value for decreasing loop	Check if the starting value for the right half is <span>i-1</span>
Input 0 or Negative Number	No data validation performed	Add <span>if (n < 1) return;</span>

🚀 Next Preview: No.7: Printing Narcissistic Numbers – Can Your Code Find All “Narcissistic Numbers”?

📢 Interaction Time

1. Can you implement the pyramid using other algorithms? Feel free to leave a comment!

2. Vote: Which implementation do you think is the most clever?

• 👍 Basic Version (Easy to Read)

• ❤️ Single Loop Version (Efficient)

• 🔥 Recursive Version (Elegant)

🚀If you find this useful, feel free to share it with friends learningC Language!

Article Author:Vv Computer Graduate World (Focusing on Computer Graduate Guidancefor 8years)

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