【HDU4919】递推java大数 递归优化

Exclusive or

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 391    Accepted Submission(s): 167

Problem Description

Given n, find the value of 


Note: ⊕ denotes bitwise exclusive-or.

 

Input

The input consists of several tests. For each tests:

A single integer n (2≤n<10⁵⁰⁰).

 

Output

For each tests:

A single integer, the value of the sum.

 

Sample Input

34

 

Sample Output

64

 

Author

Xiaoxu Guo (ftiasch)

 

Source

2014 Multi-University Training Contest 5

现在写java都是先写成c++再对着翻译，先上一份，思路跟标程类似

c++

#define DeBUG#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <cstdlib>#include <algorithm>#include <vector>#include <stack>#include <queue>#include <string>#include <set>#include <sstream>#include <map>#include <list>#include <bitset>using namespace std ;#define zero {0}#define INF 0x3f3f3f3f#define EPS 1e-6#define TRUE true#define FALSE falsetypedef long long LL;const double PI = acos(-1.0);//#pragma comment(linker, "/STACK:102400000,102400000")inline int sgn(double x){    return fabs(x) < EPS ? 0 : (x < 0 ? -1 : 1);}#define N 100005int dfs(int n){    if (n <= 2)        return 0;    if (n == 3)        return 6;    int k;    if (n & 1)    {        k = (n - 1) / 2;        return 4 * dfs(k) + 6 * k;    }    else    {        k = n / 2;        return 2 * dfs(k) + 2 * dfs(k - 1) + 4 * k - 4;    }}int contribution(int n,int coe){    int result;    if(n&1)    {        result=(n/2)*6;    }    else    {        result=n*2-4;    }    return result*coe;}struct node{    int a;    int b;};int main(){#ifdef DeBUGs    freopen("C:\\Users\\Sky\\Desktop\\1.in", "r", stdin);#endif    int n;    while (scanf("%d", &n) + 1)    {        // printf("%d\n",  dfs(n));        node val;        val.a=1;        val.b=0;        int result=0;        while(n)        {            result=result+contribution(n,val.a)+contribution(n+1,val.b);            node new_nn;                  if(n&1)            {                n=n/2;                new_nn.a=val.a*4+val.b*2;                new_nn.b=val.b*2;            }            else            {                n=n/2-1;                new_nn.a=val.a*2;                new_nn.b=val.a*2+val.b*4;            }            val=new_nn;        }        printf("%d\n", result);    }    return 0;}

java大数翻译

import java.io.*;import java.util.Scanner;import java.math.BigInteger;class Main{    public static class Node    {        BigInteger a;        BigInteger b;    }    public static BigInteger get(BigInteger  n, BigInteger coe )    {        BigInteger result;        if ((n.intValue() & 1) == 1)        {            result = n.divide(BigInteger.valueOf(2)).multiply(BigInteger.valueOf(6));        }        else        {            result = n.multiply(BigInteger.valueOf(2)).add(BigInteger.valueOf(-4));        }        return result.multiply(coe);    }    public static void main(String[]Args) throws FileNotFoundException    {        InputStream in=System.in;        // InputStream in = new FileInputStream(new File("C:\\Users\\Sky\\Desktop\\1.in"));        Scanner s = new Scanner(in);        BigInteger n;        while (s.hasNext())        {            n = s.nextBigInteger();            Node val = new Node();            val.a = BigInteger.valueOf(1);            val.b = BigInteger.valueOf(0);            BigInteger result = BigInteger.ZERO;            while (n.intValue() != 0)            {                result = result.add(get(n, val.a)).add(get(n.add(BigInteger.ONE), val.b));                Node new_val = new Node();                if ((n.intValue() & 1) == 1)                {                    n = n.divide(BigInteger.valueOf(2));                    new_val.a = val.a.multiply(BigInteger.valueOf(4)).add(val.b.multiply(BigInteger.valueOf(2)));                    new_val.b = val.b.multiply(BigInteger.valueOf(2));                }                else                {                    n = n.divide(BigInteger.valueOf(2)).add(BigInteger.ONE.negate());                    new_val.a = val.a.multiply(BigInteger.valueOf(2));                    new_val.b = val.a.multiply(BigInteger.valueOf(2)).add(val.b.multiply(BigInteger.valueOf(4)));                }                val=new_val;            }            System.out.println(result);        }    }}

直接递归写了发现很慢，后来听锋爷一个hashmap就过了~~O(∩_∩)O~~

c++版

#define DeBUG#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <cstdlib>#include <algorithm>#include <vector>#include <stack>#include <queue>#include <string>#include <set>#include <sstream>#include <map>#include <list>#include <bitset>using namespace std ;#define zero {0}#define INF 0x3f3f3f3f#define EPS 1e-6#define TRUE true#define FALSE falsetypedef long long LL;const double PI = acos(-1.0);//#pragma comment(linker, "/STACK:102400000,102400000")inline int sgn(double x){    return fabs(x) < EPS ? 0 : (x < 0 ? -1 : 1);}#define N 100005std::map<int, int> mp;int dfs(int n){    printf("%d\n", n);    if(mp[n]!=0)        return mp[n];    if (n <= 2)        return 0;    if (n == 3)        return 6;    int k;    if (n & 1)    {        k = (n - 1) / 2;            mp[n] = 4 * dfs(k) + 6 * k;        return mp[n];    }    else    {        k = n / 2;            mp[n] = 2 * dfs(k) + 2 * dfs(k - 1) + 4 * k - 4;        return mp[n];    }}int main(){#ifdef DeBUGs    freopen("C:\\Users\\Sky\\Desktop\\1.in", "r", stdin);#endif    int n;    while (scanf("%d", &n) + 1)    {        cout<<dfs(n)<<endl;    }    return 0;}

java版

import java.io.*;import java.math.BigInteger;import java.util.HashMap;import java.util.Scanner;class Main{public static BigInteger two = BigInteger.valueOf(2);public static BigInteger three = BigInteger.valueOf(3);public static BigInteger onefu = BigInteger.ONE.negate();public static HashMap<BigInteger, BigInteger>hash=new HashMap<BigInteger, BigInteger>();public static BigInteger dfs(BigInteger n){if(hash.get(n)!=null)return hash.get(n);if (n.compareTo(two) <= 0)return BigInteger.ZERO;if (n.compareTo(three) == 0)return BigInteger.valueOf(6);BigInteger k;if ((n.intValue() & 1) == 1){k = (n.add(onefu).divide(two));BigInteger now=BigInteger.valueOf(4).multiply(dfs(k)).add(BigInteger.valueOf(6).multiply(k));hash.put(n, now);return now;}else{k = n.divide(two);BigInteger now=two.multiply(dfs(k)).add(two.multiply(dfs(k.add(onefu)))).add(BigInteger.valueOf(4).multiply(k)).add(BigInteger.valueOf(-4));hash.put(n, now);return now;}}public static void main(String[] Args) throws FileNotFoundException{InputStream in = System.in;// InputStream in = new FileInputStream(new// File("C:\\Users\\Sky\\Desktop\\1.in"));Scanner s = new Scanner(in);BigInteger n;while (s.hasNext()){n = s.nextBigInteger();System.out.println(dfs(n));}}}