Analysis of the C++ Questions from the 16th Blue Bridge Cup – August 2025

1. Run the following program, the output result is ( ).

A.X0 B.X5 C.5 D.0

Knowledge points assessed: functions, local variables, and global variables.

2. Run the following program, the output result is ( ).

A.3 B.4 C.9 D.16Knowledge points assessed: simulation.i=1, satisfies the while statement, runs t=1, i=3;i=3, satisfies the while statement, runs t=2, i=5;i=5, satisfies the while statement, runs t=3, i=7;i=7, does not satisfy the while statement, outputs t=3.3. The result of the statement: cout<<(char)(‘F’+4) is ( ).A.I B.j C.K D.JKnowledge points assessed: character type operations.4. Among the following choices, the one with the highest precedence is ( ).A.+ B.- C.* D.=Knowledge points assessed: operation precedence.5. Regarding the new and delete keywords in C++, which of the following statements is incorrect ( ).

A. Memory allocated with new int[10] must be released with delete[] – Correct

B. int *p = new int; allocated integer memory is initialized to 0 by default – Incorrect (not initialized by default)

C. Using delete on a null pointer (nullptr) is safe and will not cause an error – Correct

D. new throws std::bad_alloc exception by default when memory allocation fails, rather than returning a null pointer – Correct

Based on the provided options and C++ memory management rules, the analysis is as follows:

• ‌A. Memory allocated with new int[10] must be released with delete[] – Correct‌In C++, memory allocated with<span><span>new[]</span></span>must be released with<span><span>delete[]</span></span>to ensure all memory is correctly released and destructors (if any) are called. Using regular<span><span>delete</span></span>will lead to undefined behavior. Therefore, this statement is correct.

• ‌B. int *p = new int; allocated integer memory is initialized to 0 by default – Incorrect (not initialized by default)‌This statement is incorrect. In C++,<span><span>new int</span></span>does not initialize the allocated memory, which contains undefined garbage values. If initialization to 0 is needed,<span><span>new int()</span></span>must be used (value initialization). Therefore, the original statement “allocated integer memory is initialized to 0 by default” is incorrect.

• ‌C. Using delete on a null pointer (nullptr) is safe and will not cause an error – Correct‌The C++ standard states that using<span><span>nullptr</span></span>with<span><span>delete</span></span><span><span>is safe; the operation will be ignored and will not cause a runtime error. Therefore, this statement is correct.</span></span>

• ‌D. new throws std::bad_alloc exception by default when memory allocation fails, rather than returning a null pointer – Correct‌By default,<span><span>new</span></span>throws<span><span>std::bad_alloc</span></span><span><span>exception when memory allocation fails, rather than returning a null pointer. If a null pointer is needed,</span></span><code><span><span>new (std::nothrow)</span></span><span><span>must be used. Therefore, this statement is correct.</span></span>

Conclusion

The incorrect option is ‌B‌, because<span><span>new int</span></span><span><span>allocated integer memory is not initialized to 0 by default.</span></span>

Programming 1: Celebration Queue

Programming 2: Tea Set Combination

Programming 3: Character Swap to Balance Odd and Even Positions

Programming 4: Layered Matrix Interleaved RotationAnalysis:

The 1st layer (outer layer) rotates 90 degrees clockwise.

The 2nd layer (inner layer) rotates 90 degrees counterclockwise.

Input requirements

1. The first line inputs a positive integer n (2<=n<=100), representing the number of rows and columns of the matrix

2. The next n lines, each input n integers (-1000<=integer<=1000), representing the matrix elements, separated by spaces

Output requirements

Output n lines, each line containing n integers, representing the rotated matrix, separated by spaces.

Key points

1. Layer division: process layer by layer from outside to inside,

2. Alternating rotation direction: odd layers clockwise, even layers counterclockwise.

3. Center element: if n is odd, the center element does not rotate,

Data range

Matrix size: from 2×2 to 100×100.

Element value range: -1000 to 1000,

Sample input and output

Input:

4

1 2 3 4

5 6 7 8

9 10 11 12

13 14 15 16

Output:

13 9 5 1

14 6 7 2

15 10 11 3

16 12 8 4

Programming 5: Circular Coin GameTake Coins

Example explanation

First data set (n=1,a_1=10):

Jerry takes all 10 coins, Tom cannot take any, Jerry wins.

Second data set (n=2,a_1=30, a_2=50):

Jerry and Tom take turns taking coins, ultimately Tom wins (specific strategy needs further analysis).

Programming 6: Magic Card Arrangement