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 (≤) 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#include<cstdio> #include<algorithm> using namespace std; const int maxn = 100010;int arr[maxn];int main(){int n, ans = 0;scanf("%d",&n);int left = n-1 ,num;for(int i = 0; i < n; i++){scanf("%d",&num);arr[num] = i;if(i == num && num != 0){left--;}}int k = 1;while(left > 0){if(arr[0] == 0){while(k < n){if(arr[k] != k){swap(arr[0],arr[k]);ans++;break;}k++;}}if(arr[0] != 0){swap(arr[0],arr[arr[0]]);ans++;left--;}}printf("%d",ans);return 0; }
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