📌 Problem Description
Write a function to swap the values of two integer variables.
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Example Input: a = 5, b = 10
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Example Output: a = 10, b = 5
Difficulty: ⭐ (suitable for beginners, but how many methods can you think of?)
💡 Initial Thoughts
You might think: “Isn’t this just using a temporary variable to store the value?”
But, the real challenge is:
❓ If using a temporary variable is not allowed, can you still swap the values?
❓ What methods do you know that might be tested in exams?
📝 Method1: Temporary Variable Method (Most Basic)
void swap(int *a, int *b) {int temp = *a; // Store the value of a in temp*a =*b; // Assign the value of b to a*b= temp; // Assign temp (original value of a) to b}✔️ Advantages:
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Clear logic, applicable to all data types (int, float, struct, etc.)
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No overflow issues
❌ Disadvantages:
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Uses an extra variable, occupying an additional 4 bytes of memory (but usually negligible)
🔥 Method2: Arithmetic Method (No Temporary Variable)
void swap(int *a, int *b) {*a =*a + *b; // a = a + b*b =*a - *b; // b = (a + b) - b = a*a =*a - *b; // a = (a + b) - a = b}✔️ Advantages:
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Saves one variable
- Suitable for memory-sensitive scenarios
❌ Disadvantages:
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Possible overflow! If *a + *b exceeds INT_MAX, the result will be incorrect!
⚡ Method 3: Bitwise Method (High Frequency Exam Topic)
void swap(int *a, int *b) {*a ^= *b; // a = a ^ b*b ^= *a; // b = b ^ (a ^ b) = a*a ^= *b; // a = (a ^ b) ^ a = b}✔️ Advantages:
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No overflow risk
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Bitwise operations are efficient, suitable for embedded development
❌ Disadvantages:
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Poor readability, may be difficult for those unfamiliar with bitwise operations
In-depth Analysis
| Method | Applicable Scenarios | Potential Issues |
| Temporary Variable | General, Safe | None |
| Arithmetic Operation | Saves Memory | Possible Overflow |
| Bitwise Operation | High Performance Requirement | Poor Readability |
❓ Reflection:
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Why do the formal parameters in a void function need to be pointers?
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If the values being swapped are floating-point numbers, are these methods still applicable?
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If the values being swapped are strings (char *), how would you write it?
🚀 Next Issue Preview
No.2: Using Macros (#define) to Swap Two Variables, Can You Do It?
📢 Interactive Time
1. Do you know other methods to swap variables? Feel free to leave a comment!
2. Which method do you think is the most clever? Vote:
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👍 Temporary Variable Method
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❤️ Arithmetic Method
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🔥 Bitwise Method
Friendly Reminder: This article only provides the core function implementation code. If you want to run it on a compiler, don’t forget to add the main function, and remember to pass parameters by address or pointer.
🚀 If you find this useful, feel free to share it with friends learning C Language!
Article Author: Vv Computer Graduate Exam World (Focusing on Computer Graduate Exam Tutoring for 8 years)
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