USACO Pearl Pairing
作者:互联网
洛谷 P2902 [USACO08MAR]珍珠配对Pearl Pairing
https://www.luogu.org/problem/P2902
JDOJ 2577: USACO 2008 Mar Gold 3.Pearl Pairing
https://neooj.com:8082/oldoj/problem.php?id=2577
Description
At Bessie's recent birthday party, she received N (2 <= N <= 100,000;
N%2 == 0) pearls, each painted one of C different colors (1 <= C
< = N).
Upon observing that the number of pearls N is always even, her
creative juices flowed and she decided to pair the pearls so that
each pair of pearls has two different colors.
Knowing that such a set of pairings is always possible for the
supplied testcases, help Bessie perform such a pairing. If there
are multiple ways of creating a pairing, any solution suffices.
Input
* Line 1: Two space-separated integers: N and C
* Lines 2..C + 1: Line i+1 tells the count of pearls with color i: C_i
Output
* Lines 1..N/2: Line i contains two integers a_i and b_i indicating
that Bessie can pair two pearls with respective colors a_i and
b_i.
Sample Input
8 3 2 2 4Sample Output
1 3 1 3 2 3 3 2HINT
INPUT DETAILS:
There are 8 pearls and 3 different colors. Two pearls have color I; two
have color II; four have color III.
OUTPUT DETAILS:
Bessie pairs each pearl of color III with one of color I and II.
题目大意:在Bessie最近的生日聚会上,她收到N(2<=N<=100,000; N%2==0)珍珠,每个都涂上C种不同颜色之一(1<=C<=N)。
观察到珍珠N的数量总是均匀的,她的创意来了,决定配对珍珠,使每双珍珠有两种不同的颜色。数据保证存在答案。请帮助Bessie执行这样的配对,如果有多种创建配对的方法,任意输出即可。
SPJ开了。
我是为了刷背包才看到这道题的,想破脑袋也没想出来咋背包,后来用模拟做了一遍,思路是这个样子。
既然数据保证存在答案,我们便开始思考什么样子的数据才会保证存在答案。
然后我们发现每种颜色的数量不可能超过N/2要不然没法玩。
所以我们就想出了这样一种方案:
记录下每个珍珠的颜色,然后分成两组(因为N是偶数)
由于不可能有颜色数量超过N/2,所以我们枚举N/2次,每次取两组的第i位,就可以百分百保证不会有重复。
脑筋急转弯的味道很浓,你信我的就没问题。
其实也不需要再打一遍sort,因为你存数组的时候就是从小到大存的。
代码如下:
#include<cstdio> using namespace std; int s[100001]; int n,c; int k; int main() { scanf("%d%d",&n,&c); for(int i=1;i<=c;i++) { int x; scanf("%d",&x); for(int j=1;j<=x;j++) s[++k]=i; } for(int i=1;i<=n/2;i++) printf("%d %d\n",s[i],s[i+(n/2)]); return 0; }
sort与否随你便。
标签:color,pearls,Pairing,colors,USACO,two,Pearl,int,Bessie 来源: https://www.cnblogs.com/fusiwei/p/11258171.html