14. Width and Precision Combined

📝 Problem

Accept a floating point value and print it with 20 width space and round off to 4 decimal places.

Input Format:
Accept a floating point value

Output Format:
Print the give value with width 20 and rounded off to 4 decimal places

Constraints:
2.3E-308 to 1.7E+308

💡 Combining Width and Precision

This problem combines two important formatting concepts:

setw(20) - Sets the output width to 20 characters (right-aligned by default)
setprecision(4) - With fixed, shows exactly 4 decimal places
fixed - Prevents scientific notation and enables decimal precision

📚 Want to learn more about setw()?

📖 Read Question #9: Complete Guide to setw, setfill & Alignment →

How it works together:

Visual Example (width = 20):

|----5----|----10---|----15---|----20|

Input: 12.45678

Output: 12.4568

↑ 12 spaces + 7 chars (12.4568) = 20 total width

Order matters!

✅ fixed → setprecision(4) → setw(20)
The number is first formatted with precision, then padded to width

Key Differences:

setw() - Affects total width (including decimal point and digits)
setprecision() - Only affects digits after decimal point
setw() is temporary - applies only to next output
fixed and setprecision() are persistent

Examples

Sample Input 1:

Input:

12.45678

Sample Output 1:

Output:

12.4568

Note: 12 leading spaces + "12.4568" (7 chars) = 20 total width

Sample Input 2:

Input:

19.45789

Sample Output 2:

Output:

19.4579

Note: Rounded from 19.45789 to 19.4579 (4 decimal places)

Solution.cpp

#include <iostream>
#include <iomanip>

using namespace std;

int main() {
    long double f;
    cin >> f;
    
    // fixed: Prevents scientific notation
    // setprecision(4): Exactly 4 decimal places
    // setw(20): Total width of 20 characters
    cout << fixed << setprecision(4) << setw(20) << f;
    
    return 0;
}