C++ unordered_map自定义KEY用法以及insert无法覆盖解决办法

对于自定义KEY需要重载==判断是否相等，用()获取hash值

struct	stream_order_key
{
	std::string instrument;
	ioption::TChnOrderLocalIDType orderLocalID;

	stream_order_key() : orderLocalID(0) {}

	bool operator==(const stream_order_key& s) const
	{
		return instrument==s.instrument && orderLocalID==s.orderLocalID;
	}

	size_t operator()(const stream_order_key& s) const
	{
		size_t seed = 0;
		boost::hash_combine(seed, boost::hash_value(s.instrument));
		boost::hash_combine(seed, boost::hash_value(s.orderLocalID));
		return seed;
	}

};



typedef std::unordered_map<<span style="font-family: Arial, Helvetica, sans-serif;">stream_order_key</span><span style="font-family: Arial, Helvetica, sans-serif;">, int, stream_order_key> stream_order_map;</span>

添加一个hash算法:

		inline size_t operator()(const T & ov) const
		{
			/// BKD HASH
			unsigned int seed = 131; // 31 131 1313 13131 131313 etc..
			unsigned int hash = 0;
			const char* str = ov.c_str();
			while (*str)
			{
				hash = hash * seed + (*str++);
			}

			return (hash & 0x7FFFFFFF);
		}

对于insert无法覆盖问题解决办法:

使用

stream_order_map order_map;

order_map[s] = a;

order_map[s] = b;

可以解决