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订单方向枚举

Order Side Enum

专题
Systems & Architecture / 系统与架构
难度
L1
来源
MyntBit

题目详情

在低延迟交易系统中，类型安全至关重要，防止意外混淆买卖方向。使用强类型 scoped enum 约束订单方向，配合 constexpr 函数实现零开销转换。

任务：实现买卖方向 scoped enum（BUY/SELL），提供编译期字符转换函数。运行时零开销。

英文原题

In low-latency trading systems, type safety is critical to prevent the accidental mixing of order sides, prices, and quantities. Utilizing a strongly typed scoped enumeration for order sides enforces this safety, while a constexpr function allows the compiler to evaluate the opposite side at compile time to eliminate runtime overhead.
Task
Implement a scoped enumeration enum class OrderSide containing two values: Buy = 0 and Sell = 1. Then, write a constexpr function flipSide(OrderSide side) th

解析

问题分析

使用类型安全的枚举表示订单方向（买入/卖出/做空）可以避免将整数误传为订单方向的编译期错误。C++ enum class 配合 switch 穷举检查可确保所有方向都被处理。

实现

enum class OrderSide : uint8_t { BUY = 1, SELL = 2, SHORT = 3 };
inline std::string_view toString(OrderSide s) {
    switch (s) {
        case OrderSide::BUY: return "BUY";
        case OrderSide::SELL: return "SELL";
        case OrderSide::SHORT: return "SHORT";
    }
    return "UNKNOWN";
}
inline int sign(OrderSide s) { return (s == OrderSide::BUY) ? 1 : -1; }

复杂度与边界

  • 时间复杂度：toString O(1)
  • 空间复杂度：O(1)
  • 边界条件：(1) 从整数构造时验证范围 (2) switch 无 default 分支以便编译器警告未处理枚举值

英文解析

Analysis

Type-safe enums representing order direction (buy/sell/short) prevent compile-time errors from passing integers as order directions. C++ enum class with exhaustive switch checking ensures all directions are handled.

Solution

enum class OrderSide : uint8_t { BUY = 1, SELL = 2, SHORT = 3 };
inline std::string_view toString(OrderSide s) {
    switch (s) {
        case OrderSide::BUY: return "BUY";
        case OrderSide::SELL: return "SELL";
        case OrderSide::SHORT: return "SHORT";
    }
    return "UNKNOWN";
}
inline int sign(OrderSide s) { return (s == OrderSide::BUY) ? 1 : -1; }

Complexity & Edge Cases

  • Time complexity: toString O(1)
  • Space complexity: O(1)
  • Edge cases: (1) Validate range when constructing from integer (2) No default branch in switch enables compiler warnings for unhandled enum values

Key Considerations

  1. Explicit underlying type: Use enum class : uint8_t for compact serialization; never rely on default int-sized underlying type for wire protocol
  2. Bid/Ask vs Buy/Sell: Side must distinguish direction (buy vs sell) from market position (bid vs ask); buy = bid side, sell = ask side in standard convention
  3. Serialization mapping: Map enum values to FIX Side values (1=Buy, 2=Sell) and binary protocol codes; provide bidirectional conversion functions
  4. Invalid value handling: Decoder must reject unknown side values; treat as error, not default to Buy — wrong side causes incorrect position accumulation