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cf上如何防止unordered_map被hack

发布时间 2023-08-30 17:22:01作者: north_h

打cf的时候用unordered_map防止被hack可以重新自定义哈希函数

第一种

struct custom_hash {
	static uint64_t splitmix64(uint64_t x) {
		x ^= x << 13;
		x ^= x >> 7;
		x ^= x << 17;
		return x; 
	}
	size_t operator () (uint64_t x) const {
		static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count(); // 时间戳
		return splitmix64(x + FIXED_RANDOM);
	}
};

第二种

struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};

定义

unordered_map<int, int, custom_hash> Hash;