USACO-Section 1.3 Combination Lock（枚举）

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最新推荐文章于 2023-01-02 16:37:25 发布

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介绍了一种用于破解特定类型组合锁的算法，该锁允许一定范围内的数值偏差。通过枚举所有可能接近两个预设组合（农场主设置及制造商默认组合）的设置来确定能打开锁的组合数量。

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Combination Lock

Farmer John's cows keep escaping from his farm and causing mischief. To try and prevent them from leaving, he purchases a fancy combination lock to keep his cows from opening the pasture gate.

Knowing that his cows are quite clever, Farmer John wants to make sure they cannot easily open the lock by simply trying many different combinations. The lock has three dials, each numbered 1..N (1 <= N <= 100), where 1 and N are adjacent since the dials are circular. There are two combinations that open the lock, one set by Farmer John, and also a "master" combination set by the lock maker.

The lock has a small tolerance for error, however, so it will open even if the numbers on the dials are each within at most 2 positions of a valid combination.

For example, if Farmer John's combination is (1,2,3) and the master combination is (4,5,6), the lock will open if its dials are set to (1,3,5) (since this is close enough to Farmer John's combination) or to (2,4,8) (since this is close enough to the master combination). Note that (1,5,6) would not open the lock, since it is not close enough to any one single combination.

Given Farmer John's combination and the master combination, please determine the number of distinct settings for the dials that will open the lock. Order matters, so the setting (1,2,3) is distinct from (3,2,1).

PROGRAM NAME: combo

INPUT FORMAT:

Line 1:	The integer N.
Line 2:	Three space-separated integers, specifying Farmer John's combination.
Line 3:	Three space-separated integers, specifying the master combination (possibly the same as Farmer John's combination).

SAMPLE INPUT (file combo.in):

50
1 2 3
5 6 7

INPUT DETAILS:

Each dial is numbered 1..50. Farmer John's combination is (1,2,3), and the master combination is (5,6,7).

OUTPUT FORMAT:

Line 1:

The number of distinct dial settings that will open the lock.

SAMPLE OUTPUT (file combo.out):

SAMPLE OUTPUT EXPLANATION

Here's a list:

1,1,1  2,2,4  3,4,2  4,4,5  5,4,8  6,5,6  7,5,9  3,50,2  50,1,4 
1,1,2  2,2,5  3,4,3  4,4,6  5,4,9  6,5,7  7,6,5  3,50,3  50,1,5 
1,1,3  2,3,1  3,4,4  4,4,7  5,5,5  6,5,8  7,6,6  3,50,4  50,2,1 
1,1,4  2,3,2  3,4,5  4,4,8  5,5,6  6,5,9  7,6,7  3,50,5  50,2,2 
1,1,5  2,3,3  3,4,6  4,4,9  5,5,7  6,6,5  7,6,8  49,1,1  50,2,3 
1,2,1  2,3,4  3,4,7  4,5,5  5,5,8  6,6,6  7,6,9  49,1,2  50,2,4 
1,2,2  2,3,5  3,4,8  4,5,6  5,5,9  6,6,7  7,7,5  49,1,3  50,2,5 
1,2,3  2,4,1  3,4,9  4,5,7  5,6,5  6,6,8  7,7,6  49,1,4  50,3,1 
1,2,4  2,4,2  3,5,5  4,5,8  5,6,6  6,6,9  7,7,7  49,1,5  50,3,2 
1,2,5  2,4,3  3,5,6  4,5,9  5,6,7  6,7,5  7,7,8  49,2,1  50,3,3 
1,3,1  2,4,4  3,5,7  4,6,5  5,6,8  6,7,6  7,7,9  49,2,2  50,3,4 
1,3,2  2,4,5  3,5,8  4,6,6  5,6,9  6,7,7  7,8,5  49,2,3  50,3,5 
1,3,3  3,1,1  3,5,9  4,6,7  5,7,5  6,7,8  7,8,6  49,2,4  50,4,1 
1,3,4  3,1,2  3,6,5  4,6,8  5,7,6  6,7,9  7,8,7  49,2,5  50,4,2 
1,3,5  3,1,3  3,6,6  4,6,9  5,7,7  6,8,5  7,8,8  49,3,1  50,4,3 
1,4,1  3,1,4  3,6,7  4,7,5  5,7,8  6,8,6  7,8,9  49,3,2  50,4,4 
1,4,2  3,1,5  3,6,8  4,7,6  5,7,9  6,8,7  1,50,1 49,3,3  50,4,5 
1,4,3  3,2,1  3,6,9  4,7,7  5,8,5  6,8,8  1,50,2 49,3,4  49,50,1
1,4,4  3,2,2  3,7,5  4,7,8  5,8,6  6,8,9  1,50,3 49,3,5  49,50,2
1,4,5  3,2,3  3,7,6  4,7,9  5,8,7  7,4,5  1,50,4 49,4,1  49,50,3
2,1,1  3,2,4  3,7,7  4,8,5  5,8,8  7,4,6  1,50,5 49,4,2  49,50,4
2,1,2  3,2,5  3,7,8  4,8,6  5,8,9  7,4,7  2,50,1 49,4,3  49,50,5
2,1,3  3,3,1  3,7,9  4,8,7  6,4,5  7,4,8  2,50,2 49,4,4  50,50,1
2,1,4  3,3,2  3,8,5  4,8,8  6,4,6  7,4,9  2,50,3 49,4,5  50,50,2
2,1,5  3,3,3  3,8,6  4,8,9  6,4,7  7,5,5  2,50,4 50,1,1  50,50,3
2,2,1  3,3,4  3,8,7  5,4,5  6,4,8  7,5,6  2,50,5 50,1,2  50,50,4
2,2,2  3,3,5  3,8,8  5,4,6  6,4,9  7,5,7  3,50,1 50,1,3  50,50,5
2,2,3  3,4,1  3,8,9  5,4,7  6,5,5  7,5,8

每个密码数字误差在2以内的数字最多有5个，2个密码则最多有250种结果，所以每次先找出这符合要求的数字，然后枚举即可

/*
ID: your_id_here
PROG: combo
LANG: C++
*/
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
int i,j,k,ans,n,num[105],f[3],maybe[3][5];
bool used[105][105][105];//used[i][j][k]表示这样的组合是否出现过

void cal() {
    if(n==1) {//当n为1时，不满足以下的方法，特判结果为1返回
        ans=1;
        return ;
    }
    for(i=0;i<3;++i) {//找3个密码数字符合要求的
        maybe[i][0]=f[i]-2<=0?n+f[i]-2:f[i]-2;
        maybe[i][1]=f[i]-1==0?n:f[i]-1;
        maybe[i][2]=f[i];
        maybe[i][3]=f[i]+1>n?1:f[i]+1;
        maybe[i][4]=f[i]+2>n?f[i]-n+2:f[i]+2;
    }
    for(i=0;i<5;++i)
        for(j=0;j<5;++j)
            for(k=0;k<5;++k)
                if(!used[maybe[0][i]][maybe[1][j]][maybe[2][k]]) {
                    used[maybe[0][i]][maybe[1][j]][maybe[2][k]]=true;
                    ++ans;
                }
}

int main() {
    freopen("combo.in","r",stdin);
    freopen("combo.out","w",stdout);
    while(1==scanf("%d",&n)) {
        memset(used,false,sizeof(used));
        ans=0;
        scanf("%d%d%d",f,f+1,f+2);
        cal();
        scanf("%d%d%d",f,f+1,f+2);
        cal();
        printf("%d\n",ans);
    }
    return 0;
}