算法分析之常胜将军

 

常胜将军是一个非常有意思的智力游戏趣题，常胜将军的大意如下：

甲和乙两人玩抽取火柴的游戏，共有21根火柴。每个人每次最多取4根火柴，最少取1根火柴。如果某个人取到最后一根火柴则输了。甲让乙先抽取，结果每次都是甲赢。

先来分析'下常胜将军问题。甲要每次都赢，那么每次甲给乙只剩下1根火柴，因为此时乙至少取1根火柴，这样才能保证甲常胜。由于乙先抽取，因此只要保证甲抽取的数量和乙抽取的数量之和为5即可。

namespace section10_generalWin{
void generalWin(int last){
    int computer,user;
    while(1){
        printf("The current number of matchstick is %d.
",last);
        printf("How many matchsticks do you choose?
");
        scanf("%d",&user);
        printf("Your choose %d matchsticks
",user);
        if(user<1||user>4||user>last){
            printf("You have been fault! Please input your choice again!
");
            continue;
        }
        last=last-user;
        if(last==0){
            printf("The comupter has become a winner!
");
            break;
        }else{
            computer=5-user;
            last=last-computer;
            printf("The computer chooses %d matchstick!
",computer);
            if(last==0){
                printf("The user has become a winner!
");
                break;
            }
        }
    }
}

void runGeneral(){
    int last;
    printf("Please input the total number of matchstick!
");
    scanf("%d",&last);
    generalWin(last);
}