• POJ2960S-Nim


            Arthur and his sister Caroll have been playing a game called Nim for some time now. Nim is played as follows:
    • The starting position has a number of heaps, all containing some, not necessarily equal, number of beads.
    • The players take turns chosing a heap and removing a positive number of beads from it.
    • The first player not able to make a move, loses.
    Arthur and Caroll really enjoyed playing this simple game until they
    recently learned an easy way to always be able to find the best move:
    • Xor the number of beads in the heaps in the current position (i.e. if we have 2, 4 and 7 the xor-sum will be 1 as 2 xor 4 xor 7 = 1).
    • If the xor-sum is 0, too bad, you will lose.
    • Otherwise, move such that the xor-sum becomes 0. This is always possible.
    It is quite easy to convince oneself that this works. Consider these facts:
    • The player that takes the last bead wins.
    • After the winning player's last move the xor-sum will be 0.
    • The xor-sum will change after every move.
    Which means that if you make sure that the xor-sum always is 0 when you have made your move, your opponent will never be able to win, and, thus, you will win.

    Understandibly it is no fun to play a game when both players know how to play perfectly (ignorance is bliss). Fourtunately, Arthur and Caroll soon came up with a similar game, S-Nim, that seemed to solve this problem. Each player is now only allowed to remove a number of beads in some predefined set S, e.g. if we have S = {2, 5} each player is only allowed to remove 2 or 5 beads. Now it is not always possible to make the xor-sum 0 and, thus, the strategy above is useless. Or is it?

    your job is to write a program that determines if a position of S-Nim is a losing or a winning position. A position is a winning position if there is at least one move to a losing position. A position is a losing position if there are no moves to a losing position. This means, as expected, that a position with no legal moves is a losing position.

    Input

    Input consists of a number of test cases.
    For each test case: The first line contains a number k (0 < k ≤ 100) describing the size of S, followed by k numbers si (0 < si ≤ 10000) describing S. The second line contains a number m (0 < m ≤ 100) describing the number of positions to evaluate. The next m lines each contain a number l (0 < l ≤ 100) describing the number of heaps and l numbers hi (0 ≤ hi ≤ 10000) describing the number of beads in the heaps.
    The last test case is followed by a 0 on a line of its own.

    Output

    For each position: If the described position is a winning position print a 'W'.If the described position is a losing position print an 'L'.
    Print a newline after each test case.

    Sample Input

    2 2 5
    3
    2 5 12
    3 2 4 7
    4 2 3 7 12
    5 1 2 3 4 5
    3
    2 5 12
    3 2 4 7
    4 2 3 7 12
    0

    Sample Output

    LWW
    WWL

    本来想着每组数据打一次表时间更短,没想到TLE了,哎,还是每个测试样例打一次表吧,直接按最大打表出来
    #include <iostream>
    #include <cstdio>
    #include <cstring>
    #include <algorithm>
    #include <cmath>
    #define LL long long
    using namespace std;
    LL x,y;
    int n;
    int t;
    int l;
    int a[10010];
    int f[110];
    int sg[10010];
    int vis[10010];
    void getSG(int MAX)
    {
        memset(sg,0,sizeof(sg));
        for(int i = 1; i < MAX; i++)
        {
            memset(vis,0,sizeof(vis));
            for(int j = 0; f[j] <= i&&j<n; j++)
            {
                vis[sg[i-f[j]]] = 1;
            }
            for(int k = 0; ;k++)
            {
                if(!vis[k])
                {
                    sg[i] = k;
                    break;
                }
            }
        }
    }
    void debug()
    {
        for(int i = 0; i < 20; i++)
            printf("%d
    ",sg[i]);
    }
    int main()
    {
        while(scanf("%d",&n)!=EOF&&n)
        {
            for(int i = 0; i < n; i++)
                scanf("%d",&f[i]);
            sort(f,f+n);
            scanf("%d",&t);
            getSG(10010);
            while(t--)
            {
                scanf("%d",&l);
                int maxn = -1;
                for(int i = 0; i < l; i++)
                {
                    scanf("%d",&a[i]);
                    if(a[i]>maxn)
                        maxn = a[i];
                }
                //debug();
                LL ans = 0;
                for(int i = 0; i < l; i++)
                {
                    ans^=sg[a[i]];
                }
                if(ans==0)
                    printf("L");
                else
                    printf("W");
            }
            printf("
    ");
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/--lr/p/8974927.html
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