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 = ;
int pos[maxn];
int main(){
int n,ans = ;
scanf("%d",&n);
int left = n - ,num;
for(int i = ; i < n; i++){
scanf("%d",&num);
pos[num] = i;
if(num == i && num != ){
left--;
}
}
int k = ;
while(left > ){
if(pos[] == ){
while(k < n){
if(pos[k] != k){
swap(pos[],pos[k]);
ans++;
break;
}
k++;
}
}
if(pos[] != ){
swap(pos[],pos[pos[]]);
ans++;
left--;
}
}
printf("%d",ans);
return ;
}