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  • 题解 P3938 【斐波那契】

    题目链接

    Solution 斐波那契

    题目大意:兔子按照斐波那契提出的模型繁衍,根据它们的父子关系形成一棵树。每次给定两个点,求出它们的 (lca)

    贪心


    分析:首先暴力建树肯定是会直接上天的

    我们发现,对于任何一个不为根的节点,它和它的父亲编号的差值是一个斐波那契数。

    证明可以参考 斐波那契进制LeetCode 类似问题的题解我是Graphviz找规律发现的

    因此,对于一个数,我们减去它在斐波那契数列里面的前驱,就可以得到它的父亲。

    树高不超过 (60),直接暴力求 (lca) 就可以了。

    #include <cstdio>
    #include <cctype>
    #include <algorithm>
    #include <vector>
    #pragma GCC optmize(2)
    using namespace std;
    typedef long long ll;
    struct IO{//-std=c++11,with cstdio and cctype
    	private:
    		static constexpr int ibufsiz = 1 << 20;
    		char ibuf[ibufsiz + 1],*inow = ibuf,*ied = ibuf;
    		static constexpr int obufsiz = 1 << 20;
    		char obuf[obufsiz + 1],*onow = obuf;
    		const char *oed = obuf + obufsiz;
    	public:
    		inline char getchar(){
    			#ifndef ONLINE_JUDGE
    				return ::getchar();
    			#else
    				if(inow == ied){
    					ied = ibuf + sizeof(char) * fread(ibuf,sizeof(char),ibufsiz,stdin);
    					*ied = '';
    					inow = ibuf;
    				}
    				return *inow++;
    			#endif
    		}
    		template<typename T>
    		inline void read(T &x){
    			static bool flg;flg = 0;
    			x = 0;char c = getchar();
    			while(!isdigit(c))flg = c == '-' ? 1 : flg,c = getchar();
    			while(isdigit(c))x = x * 10 + c - '0',c = getchar();
    			if(flg)x = -x;
    		}
    		template <typename T,typename ...Y>
    		inline void read(T &x,Y&... X){read(x);read(X...);}
    		inline int readi(){static int res;read(res);return res;}
    		inline long long readll(){static long long res;read(res);return res;}
    		
    		inline void flush(){
    			fwrite(obuf,sizeof(char),onow - obuf,stdout);
    			fflush(stdout);
    			onow = obuf;
    		}
    		inline void putchar(char c){
    			#ifndef ONLINE_JUDGE
    				::putchar(c);
    			#else
    				*onow++ = c;
    				if(onow == oed){
    					fwrite(obuf,sizeof(char),obufsiz,stdout);
    					onow = obuf;
    				}
    			#endif
    		}
    		template <typename T>
    		inline void write(T x,char split = ''){
    			static unsigned char buf[64];
    			if(x < 0)putchar('-'),x = -x;
    			int p = 0;
    			do{
    				buf[++p] = x % 10;
    				x /= 10;
    			}while(x);
    			for(int i = p;i >= 1;i--)putchar(buf[i] + '0');
    			if(split != '')putchar(split);
    		}
    		inline void lf(){putchar('
    ');}
    		~IO(){
    			fwrite(obuf,sizeof(char),onow - obuf,stdout);
    		}
    }io;
    
    constexpr ll fib[] = {1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,1597,2584,4181,6765,10946,17711,28657,46368,75025,121393,196418,317811,514229,832040,1346269,2178309,3524578,5702887,9227465,14930352,24157817,39088169,63245986,102334155,165580141,267914296,433494437,701408733,1134903170,1836311903,2971215073,4807526976,7778742049,12586269025,20365011074,32951280099,53316291173,86267571272,139583862445,225851433717,365435296162,591286729879,956722026041,1548008755920};
    
    vector<ll> veca,vecb,tmp;
    inline void resolve(vector<ll> &vec,ll x){
    	tmp.clear();vec.clear();
    	x--;
    	while(x){
    		const ll now = *prev(upper_bound(begin(fib),end(fib),x));
    		tmp.push_back(now);
    		x -= now; 
    	}
    	reverse(tmp.begin(),tmp.end());
    	ll now = 1;
    	vec.push_back(now);
    	for(auto x : tmp){
    		now += x;
    		vec.push_back(now);
    	}
    }
    inline void solve(){
    	const ll a = io.readll(),b = io.readll();
    	if(a == b){
    		io.write(a,'
    ');
    		return;
    	}
    	resolve(veca,a);
    	resolve(vecb,b);
    	// for(auto x : veca)io.write(x,' ');
    	// io.lf();
    	// for(auto x : vecb)io.write(x,' ');
    	// io.lf();
    	for(unsigned int i = 0;;i++){
    		if(veca[i + 1] != vecb[i + 1] || (i + 1 == veca.size()) || (i + 1 == vecb.size())){
    			io.write(veca[i],'
    ');
    			return;
    		}
    	}
    }
    int main(){
    #ifndef ONLINE_JUDGE
    	freopen("fafa.in","r",stdin);
    #endif
    	const int m = io.readi();
    	for(int i = 1;i <= m;i++)solve();
    	return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/colazcy/p/14031975.html
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