HDU 2509 Be the Winner (Nim博弈)

Problem Description
Let's consider m apples divided into n groups. Each group contains no more than 100 apples, arranged in a line. You can take any number of consecutive apples at one time.
For example "@@@" can be turned into "@@" or "@" or "@ @"(two piles). two people get apples one after another and the one who takes the last is
the loser. Fra wants to know in which situations he can win by playing strategies (that is, no matter what action the rival takes, fra will win).


Input
You will be given several cases. Each test case begins with a single number n (1 <= n <= 100), followed by a line with n numbers, the number of apples in each pile. There is a blank line between cases.


Output
If a winning strategies can be found, print a single line with "Yes", otherwise print "No".


Sample Input

2
2 2
1
3



Sample Output

No

Yes

尼姆博弈变形，最后苹果数为1的堆要单独考虑。。。

以下AC代码：

#include <stdio.h>#include <string.h>int main(){    int n,i;    int flag;    int sum;    int a[55];    while(~scanf("%d",&n))    {        sum=0;        flag=0;        for(i=0;i<n;i++)        {            scanf("%d",&a[i]);            flag^=a[i];            if(a[i]>=2)                sum++;          //记录苹果数不为1的堆得堆数        }       if (!flag)    //奇异局势       {           if(sum<=1)            printf("Yes\n");           else            printf("No\n");       }       else  //非奇异局势       {       if(sum>=1)        printf("Yes\n");       else        printf("No\n");       }    }    return 0;}

Source
ECJTU 2008 Autumn Contest