对结构体数组执行排序与二分查找，附相关代码片段

Looks like you're working on sorting an array of Data structs with multi-level criteria and setting up for binary search! Let's clean up your code and walk through how to make it work properly.

First, here's your struct definition formatted clearly:

#include <string>
using namespace std; // Assuming this is included for the string type

typedef struct Data{
    int date;
    string currency;
    string exchange;
    float low;
    float high;
    long long int daily_cap;
} Data;

Next, let's fix and present your comparator functions. I noticed comp1 was cut off—here's the complete version that implements your intended multi-key sorting logic:

// Comparator for sorting by date only
bool comp2(const Data* data1, const Data* data2){
    return data1->date < data2->date;
}

// Multi-key comparator: sort by date first, then currency, then exchange
bool comp1(const Data* data1, const Data* data2){
    if (data1->date != data2->date)
        return data1->date < data2->date;
    if (data1->currency != data2->currency)
        return data1->currency < data2->currency;
    // Complete the final sorting condition for exchange
    return data1->exchange < data2->exchange;
}

Using the Comparators for Sorting #

Since you're using C++ (evidenced by the string type), you can leverage the standard sort function from the <algorithm> library. Here's how to apply it to a vector of Data pointers:

#include <algorithm>
#include <vector>

int main() {
    vector<Data*> dataCollection;
    // Populate dataCollection with your Data objects...

    // Sort using the multi-key comparator (date → currency → exchange)
    sort(dataCollection.begin(), dataCollection.end(), comp1);

    // Or sort by date only if that's your priority
    sort(dataCollection.begin(), dataCollection.end(), comp2);

    return 0;
}

Setting Up Binary Search #

For binary search to work correctly, your array must be sorted with the same logic you use for the search. Here's an example of searching for a Data object by date in a date-sorted array:

// Search for a Data* with a specific target date
Data* findByDate(vector<Data*>& sortedArray, int targetDate) {
    auto it = lower_bound(sortedArray.begin(), sortedArray.end(), targetDate,
        [](const Data* data, int date) {
            return data->date < date;
        });

    if (it != sortedArray.end() && (*it)->date == targetDate) {
        return *it;
    }
    return nullptr; // Return null if no match is found
}

If you need to search using the full multi-key criteria (date + currency + exchange), create a dummy Data struct with your target values and use comp1 to compare against elements in the sorted array.

Just a critical reminder: Always ensure your array is sorted with the exact comparator logic you use for binary search—mismatched logic will break the search functionality!

内容的提问来源于stack exchange，提问作者Sam