PAT甲级——A1067 Sort with Swap(0, i)

Posted 2022-06-13 zzw1024

Given any permutation of the numbers 0, 1, 2,..., N−1, it is easy to sort them in increasing order. But what if Swap(0, *) is the ONLY operation that is allowed to use? For example, to sort 4, 0, 2, 1, 3 we may apply the swap operations in the following way:

Swap(0, 1) => 4, 1, 2, 0, 3
Swap(0, 3) => 4, 1, 2, 3, 0
Swap(0, 4) => 0, 1, 2, 3, 4

Now you are asked to find the minimum number of swaps need to sort the given permutation of the first Nnonnegative integers.

Input Specification:

Each input file contains one test case, which gives a positive N (≤) followed by a permutation sequence of 0, 1, ..., N−1. All the numbers in a line are separated by a space.

Output Specification:

For each case, simply print in a line the minimum number of swaps need to sort the given permutation.

Sample Input:

10
3 5 7 2 6 4 9 0 8 1

Sample Output:

9

 1 #include <iostream>
 2 using namespace std;
 5 int m = 0, N, nums[100005], flag = 1, index = 1;
 6 int main()
 7 
 8     cin >> N;
 9     for (int i = 0; i < N; ++i)
10         cin >> nums[i];
11 
12     while (index<N)
13     
14         while (nums[0] != 0)
15         
16             swap(nums[0], nums[nums[0]]);
17             ++m;
18         
19         for (; index < N; ++index)//使用index，不用每次从0开始遍历
20         
21             if (index != nums[index])
22             
23                 swap(nums[0], nums[index]);
24                 ++m;
25                 break;
26             
27                 
28     
29     cout << m << endl;
30     return 0;
31