Python: Find all n-digit integers that start or end with 2

Last update on April 17 2025 13:02:36 (UTC/GMT +8 hours)

Find n-Digit Integers Starting or Ending with 2

Write a Python program to find all n-digit integers that start or end with 2.

Input: 1
Output:
[2]

Input: 2
Output:
[12, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 32, 42, 52, 62, 72, 82, 92]

Input: 3
Output:
[102, 112, 122, 132, 142, 152, 162, 172, 182, 192, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 302, 312, 322, 332, 342, 352, 362, 372, 382, 392, 402, 412, 422, 432, 442, 452, 462, 472, 482, 492, 502, 512, 522, 532, 542, 552, 562, 572, 582, 592, 602, 612, 622, 632, 642, 652, 662, 672, 682, 692, 702, 712, 722, 732, 742, 752, 762, 772, 782, 792, 802, 812, 822, 832, 842, 852, 862, 872, 882, 892, 902, 912, 922, 932, 942, 952, 962, 972, 982, 992]

Visual Presentation:

Python: Find all n-digit integers that start or end with 2.

Sample Solution:

Python Code:

# Define a function named 'test' that takes an integer 'n' as a parameter
def test(n):
    # Initialize an empty list to store the results
    ans = []
    
    # Iterate through all n-digit integers
    for i in range(10 ** (n - 1), 10 ** n):
        # Assert that the length of the current integer is equal to 'n'
        assert len(str(i)) == n
        
        # Check if the integer starts or ends with '2'
        if str(i).startswith("2") or str(i).endswith("2"):
            ans.append(i)
    
    # Return the list of integers that meet the specified conditions
    return ans

# Example 1
n1 = 1
print("Number:", n1)
print("All", n1, "- digit integers that start or end with 2:")
print(test(n1))

# Example 2
n2 = 2
print("\nNumber:", n2)
print("All", n2, "- digit integers that start or end with 2:")
print(test(n2))

# Example 3
n3 = 3
print("\nNumber:", n3)
print("All", n3, "- digit integers that start or end with 2:")
print(test(n3))

Sample Output:

Number: 1
All 1 - digit integers that start or end with 2:
[2]

Number: 2
All 2 - digit integers that start or end with 2:
[12, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 32, 42, 52, 62, 72, 82, 92]

Number: 3
All 3 - digit integers that start or end with 2:
[102, 112, 122, 132, 142, 152, 162, 172, 182, 192, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 302, 312, 322, 332, 342, 352, 362, 372, 382, 392, 402, 412, 422, 432, 442, 452, 462, 472, 482, 492, 502, 512, 522, 532, 542, 552, 562, 572, 582, 592, 602, 612, 622, 632, 642, 652, 662, 672, 682, 692, 702, 712, 722, 732, 742, 752, 762, 772, 782, 792, 802, 812, 822, 832, 842, 852, 862, 872, 882, 892, 902, 912, 922, 932, 942, 952, 962, 972, 982, 992]

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to generate all n-digit integers that either start with or end with the digit 2.
Write a Python program to filter a range of n-digit numbers and return those that begin or finish with 2.
Write a Python program to use string slicing to determine if an n-digit integer starts or ends with 2 and collect them.
Write a Python program to implement a function that returns all n-digit numbers meeting the start/end condition, sorted numerically.

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Python Code Editor :

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