Efficient itoa Implementation

itoa is a function that converts an integer to string. Your task today is to implement an itoa function that is as efficient as possible.

Some Interesting Optimizations

Small String Optimization

std::string uses Small String Optimization (SSO) to store small strings in the stack. This performance optimization avoids heap allocations for small strings. std::string contains a pointer to a buffer and a size. When the string is small, instead of allocating a new buffer on the heap, the string is stored in the pointer to the buffer instead. So, the structure looks like this:

struct string {
    union {
        char* data; // pointer to the buffer
        char buffer[16]; // buffer for small strings
    };
    size_t size;
};

This allows for small strings to be stored in the stack and avoids heap allocations and indirection.

Branch Prediction

Branch mispredictions are expensive for CPUs. You should avoid unpredictable branches in tight loops.

Expensive Operations

Operations like division and modulo are expensive for CPUs. You should avoid reduce their frequency as much as possible.

Implement an efficient itoa function in C++ that converts an integer to a string. Your implementation should handle negative numbers, minimize memory allocations, and be optimized for performance.

#include <string>
#include <algorithm>

// INPUT RANGE: std::numeric_limits<int>::min() to std::numeric_limits<int>::max()
std::string efficient_itoa(int value) {
    // TODO: Implement the most efficient itoa function
    return "";
}