新手求助：如何编写程序按数字/字母顺序输出整数或字符串？

Hey there! It's totally normal to hit this roadblock as a new programmer—let's figure out what's wrong with your current code and get you sorting correctly.

The Core Issue: a<b<c Doesn't Work Like You Think #

In C++, expressions like a<b<c don't check if a is less than b AND b is less than c. Instead, it evaluates left to right:

1. First, it calculates a<b, which returns a boolean value (true becomes 1, false becomes 0)
2. Then it compares that 0/1 value to c
3. This leads to totally incorrect logic (e.g., 1<3<2 would evaluate to true<2 → 1<2 → true, so your code would output 1,3,2 even though 3 isn't less than 2)

Fix 1: Correct If-Else Logic (Manual Sorting) #

To properly check each possible order, you need to use logical AND (&&) to combine conditions, and use else if to ensure only one block runs. Here's how to rewrite your integer sorting code:

#include <iostream>
#include <string>
using namespace std;

int main() {
    cout << "Enter three whole numbers" << endl;
    int a,b,c;
    cin >> a >> b >> c;

    if (a <= b && b <= c) {
        cout << a << "," << b << "," << c << endl;
    } else if (a <= c && c <= b) {
        cout << a << "," << c << "," << b << endl;
    } else if (b <= a && a <= c) {
        cout << b << "," << a << "," << c << endl;
    } else if (b <= c && c <= a) {
        cout << b << "," << c << "," << a << endl;
    } else if (c <= a && a <= b) {
        cout << c << "," << a << "," << b << endl;
    } else { // c <= b && b <= a
        cout << c << "," << b << "," << a << endl;
    }

    return 0;
}

Fix 2: Use the Standard Sort Function (Simpler!) #

For a cleaner approach (especially if you might sort more than 3 items later), you can put your values into an array and use the sort function from the <algorithm> library. This works for both integers and strings!

Integer Version: #

#include <iostream>
#include <algorithm> // Required for sort()
using namespace std;

int main() {
    cout << "Enter three whole numbers" << endl;
    int nums[3];
    cin >> nums[0] >> nums[1] >> nums[2];

    sort(nums, nums + 3); // Sorts the array in ascending order

    cout << nums[0] << "," << nums[1] << "," << nums[2] << endl;
    return 0;
}

String Version: #

If you want to sort strings instead, just swap the type to string—the logic is identical because C++ lets you compare strings with < directly:

#include <iostream>
#include <algorithm>
#include <string>
using namespace std;

int main() {
    cout << "Enter three strings" << endl;
    string strs[3];
    cin >> strs[0] >> strs[1] >> strs[2];

    sort(strs, strs + 3);

    cout << strs[0] << "," << strs[1] << "," << strs[2] << endl;
    return 0;
}

Key Takeaways #

• Always use && when you need to check multiple conditions (like "a is less than b AND b is less than c")
• The standard sort function is a huge time-saver once you understand it—no need to write all those if-else blocks!
• String comparison in C++ works just like numeric comparison with <, so sorting strings uses the same logic.

内容的提问来源于stack exchange，提问作者Sebastian Blake