1067. Sort with Swap(0,*) (25)

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 N nonnegative integers.

Input Specification:

Each input file contains one test case, which gives a positive N (<=10⁵) 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

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#include<iostream>#include<vector>using namespace std;int main(){    int num[100005];    int n,t,c=0;    cin>>n;    for (int i=0;i<n;i++)    {        cin>>t;        num[t]=i;    }    int sum=0;    while(c<n)    {        if (num[0]==0)        {            for (c;c<n&&c==num[c];++c)                continue;            if (c>=n)                break;            swap(num[0],num[c]);            sum++;        }        else        {           swap(num[0],num[num[0]]);            sum++;        }    }    cout<<sum;    return 0;}