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
#include<iostream> #include<algorithm> using namespace std; int n; int find(int *arr,int s,int e) { for(int i=s;i<e;i++) { if(arr[i]!=i) { return i; } } return 0; } void swap(int &a,int &b) { int temp; temp=a; a=b; b=temp; } int main() { int cnt=0,temp; cin>>n; int * a=new int[n]; for(int i=0;i<n;i++) { cin>>temp; a[temp]=i;//因为这样查找temp时间复杂度最少 } int pos=1; pos=find(a,1,n); while(pos) { if(a[0]==0) { a[0]=a[pos]; a[pos]=0; cnt++; } while(a[0]!=0) { temp=a[0]; a[0]=a[temp]; a[temp]=temp; cnt++; } pos=find(a,pos,n); } cout<<cnt<<endl; return 0; }
不知道怎么证明是cnt最小的