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PTA数据结构第一章

林塬 2022-01-08 阅读 53

时间复杂度


1-1
The Fibonacci number sequence {FN​} is defined as: F0​=0, F1​=1, FN​=FN−1​+FN−2​, N=2, 3, … The time complexity of the function which calculates FN​ recursively is Θ(N!).

  • T
  • F

1-2

(logn)2 is O(n).

  • T
  • F

1-4

NlogN2 and NlogN3 have the same speed of growth.

  • T
  • F

1-5

N2logN和NlogN2具有相同的增长速度。

  • T
  • F

1-6

2N和NN具有相同的增长速度。

  • T
  • F

2-5

求整数n(n>=0)的阶乘的算法如下,其时间复杂度为( )。

long fact(long n)
{
if (n<=1) return 1;
return n*fact(n-1);
}

  • O(n)

2-7

For the following function (where n>0)

int func ( int n )
{ int i = 1, sum = 0;
while ( sum < n ) { sum += i; i *= 2; }
return i;
}

the most accurate time complexity bound is:

  • O(logn)

2-8

For the following function (where n>0)

int func ( int n )
{ int i = 1, sum = 0;
while ( n > sum ) { i *= 2; sum += i; }
return i;
}

the most accurate time complexity bound is:

  • O(logn)

2-9

Suppose A is an array of length N with some random numbers. What is the time complexity of the following program in the worst case?

void function( int A[], int N ) {
int i, j = 0, cnt = 0;
for (i = 0; i < N; ++i) {
for (; j < N && A[j] <= A[i]; ++j);
cnt += j - i;
}
}

  • ?

算法概论


1-3

An algorithm may or may not require input, but each algorithm is expected to produce at least one result as the output.

  • T
  • F
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