pat--Sort with Swap(0, i)

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https://pta.patest.cn/pta/test/1317/exam/4/question/18076

Given any permutation of the numbers {0, 1, 2,..., N-1N−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 NN nonnegative integers.

Input Specification:

Each input file contains one test case, which gives a positive NN (\le 10^5≤10​5​​) followed by a permutation sequence of {0, 1, ..., N-1N−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:

103 5 7 2 6 4 9 0 8 1

Sample Output:

9

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#include<iostream>#include<stdio.h>using namespace std;int mark[100005];int main(){    int N,k=0,A[100005];    cin>>N;    for(int i=0; i<N; i++)    {        scanf("%d",&A[i]);        if(A[i]==i)            k++;    }    int sum=0;    for(int i=0; i<N; i++)    {        int j=i;        if(!mark[i]&&j!=A[j])        {            sum=sum+1;            while(j!=A[j]&&!mark[j])            {                mark[j]=1;                j=A[j];            }        }    }    int num=0;    if(A[0]==0)    {        num=(N-k)+sum;    }    else    {        num=(N-k)-1+(sum-1);    }    cout<<num<<endl;    return 0;}

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