2024-09-18 06:09:17 +00:00
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# CCF 2019 CSP-S 初赛题目
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## 单项选择
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### 1.D
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```
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3.5f
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```
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### 2.C
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2024-09-18 06:45:36 +00:00
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### 3.D
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2024-09-18 06:09:17 +00:00
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```
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11101110010111
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01011011101011
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11111111111111
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```
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### 4.B
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### 5.B
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### 6.B
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#### 一，1，2，4，8 = $P^4_4 = $ 24
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#### 二，1,1,8,8 = ${P^4_4\over P^2_2 \times P^2_2}=6 $
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#### 三，1，1，X，X (x=2,4,8) = $C_3^2\times{P^4_4\over P^2_2} = 36$
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#### 四，8，8，X，X (x=1,2,4) = 36
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求和得 102
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### 7.C
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插入，归并，冒泡是稳定的
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### 8.B
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将一个点排除在外
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其他的点求完全图
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完全图有n个点时
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边数 = $n\times(n-1)\over 2$
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ans=n+1
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$$
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{n\times(n-1)\over2} = 28
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$$
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得n=8
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ans=9
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### 9.B
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只考虑前三个数，后两个数是自然推出来的
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先考虑第三个数是什么
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中间这个数必须正反相同
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只有0，1，8是正反相同的
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能被3整除的数各位上的和能被3整除
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1. 中间的数是0,11种
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1. 第一位+第二位是三的倍数
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2. 00,18,81,06,60,96,69,90,09,66,99
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2. 中间的数是1，7
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1. (第一位+第二位)%3=1
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2. A*10+B,(A+B)%3=1
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3. 10,01,16,61,19,91,88
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3. 中间的数是2，7
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1. 80,08,86,68,89,98,11
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4. 求和得25种
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### 10.A
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15+12-4 = 23
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### 11.D
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1,3,5
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2,4,6
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1,2 2,3 3,4 4,5 5,6
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2n-1
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### 12.D
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储存图的两种方式，最普遍
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1. 邻接表（动态扩容的vector）
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2. 邻接矩阵（二维数组）
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### 13.B
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迪杰斯特拉:用来求由**起始点**到任意一点的距离：未优化的时间复杂度:O(n^2)贪心
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弗洛伊德:**任意两点**间的最短路径 : O(n^3) ，动态规划
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Prim:最小生成树算法（贪心）枚举每个点来找到最小生成树
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Kruskal:最小生成树算法（贪心） 枚举每个边
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### 14.B
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等比数列
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$$
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a_n = a_1\times r^{n-1}
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$$
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a1 = 2
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$a_n=a_1\times r^{n-1}$ = 118098
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$a_{b+1\over 2} = a_1 \times r^{{b+1\over 2}-1} = 486$
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$r^{n-1}=118098/2 = 59049$
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$r^{{b+1\over 2}-1}=243$
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$r^{{b+1\over 2}}=243$
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三的倍数 $3^5$=243
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### 15. A
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