A. SwapSort

 

http://codeforces.com/contest/489/problem/A

 

看样例不难发现，对于i，找到 i<=j<=n-1里最小的数，若有与i交换

 1     public static void main(String[] args) {
 2         Scanner io = new Scanner(System.in);
 3         int n = io.nextInt();
 4         int[] a = new int[n];
 5         for (int i = 0; i < n; i++) a[i] = io.nextInt();
 6         int ans = 0;
 7         ArrayList<int[]> ans2 = new ArrayList<>();
 8         for (int i = 0; i < n; i++){
 9             int min=a[i],index=-1;
10             for (int j = i + 1; j < n; j++) if (a[j]<min){min=a[j];index=j;}
11             if (index!=-1){
12                 ans++;
13                 ans2.add(new int[]{i,index});
14                 int t=a[i];a[i]=a[index];a[index]=t;
15             }
16         }
17         System.out.println(ans);
18         for (int[] aa : ans2) System.out.println(aa[0] + " " + aa[1]);
19     }