Problem: 2052A - Adrenaline Rush
Language: java

Solution 1 (runtime: 749 ms):
import java.io.*;
import java.util.*;

public class Main {
    public static int INF = 0x3f3f3f3f, mod = 1000000007, mod9 = 998244353;
    public static void main(String args[]){
        try {
            PrintWriter o = new PrintWriter(System.out);
            boolean multiTest = false;
            // init
            if(multiTest) {
                int t = nextInt(), loop = 0;
                while (loop < t) {loop++;solve(o);}
            } else solve(o);
            o.close();
        } catch (Exception e) {e.printStackTrace();}
    }
    static void solve(PrintWriter o) {
        try {
            int n = nextInt();
            int[] c = new int[n];
            for(int i=0;i<n;i++) c[i] = nextInt();
            List<int[]> li = new ArrayList<>();
            int[] a = new int[n];
            Map<Integer, Integer> idxMap = new HashMap<>();
            for(int i=0;i<n;i++) {
                a[i] = i+1;
                idxMap.put(a[i], i);
            }
            for(int i=n-1;i>=0;i--) {
                int x = idxMap.get(c[i]);
                for(int j=x-1;j>=0;j--) li.add(new int[]{a[x], a[j]});
                for(int j=0;j<x;j++) li.add(new int[]{a[j], a[x]});
                for(int j=x+1;j<i+1;j++) {
                    a[j-1] = a[j];
                    idxMap.put(a[j], j-1);
                    li.add(new int[]{a[j], c[i]});
                }
                a[i] = c[i];
                idxMap.put(c[i], i);
            }
            o.println(li.size());
            for(int[] it: li) o.println(it[0] + " " + it[1]);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static int upper_bound(List<Integer> a, int val){
        int l = 0, r = a.size();
        while(l < r){
            int mid = l + (r - l) / 2;
            if(a.get(mid) <= val) l = mid + 1;
            else r = mid;
        }
        return l;
    }
    public static int lower_bound(List<Integer> a, int val){
        int l = 0, r = a.size();
        while(l < r){
            int mid = l + (r - l) / 2;
            if(a.get(mid) < val) l = mid + 1;
            else r = mid;
        }
        return l;
    }
    public static long gcd(long a, long b){
        return b == 0 ? a : gcd(b, a%b);
    }
    public static long lcm(long a, long b){
        return a / gcd(a,b)*b;
    }
    public static long qpow(long a, long n, int md){
        a %= md;
        long ret = 1l;
        while(n > 0){
            if((n & 1) == 1){
                ret = ret * a % md;
            }
            n >>= 1;
            a = a * a % md;
        }
        return ret;
    }
    public static class FenWick {
        int n;
        long[] a;
        long[] tree;
        public FenWick(int n){
            this.n = n;
            a = new long[n+1];
            tree = new long[n+1];
        }
        private void add(int x, long val){
            while(x <= n){
                tree[x] += val;
                x += x&-x;
            }
        }
        private void addMx(int x, long val) {
            a[x] += val;
            tree[x] = a[x];
            while(x <= n) {
                for(int i=1;i<(x&-x);i<<=1) {
                    tree[x] = Math.max(tree[x], tree[x-i]);
                }
                x += x&-x;
            }
        }
        private long query(int x){
            long ret = 0l;
            while(x > 0){
                ret += tree[x];
                x -= x&-x;
            }
            return ret;
        }
        private long queryMx(int l, int r) {
            long res = 0l;
            while(l <= r) {
                if(r-(r&-r) >= l) {
                    res = Math.max(res, tree[r]);
                    r -= r&-r;
                }
                else {
                    res = Math.max(res, a[r]);
                    r--;
                }
            }
            return res;
        }
    }
    public static class Pair{
        Integer c1;
        Integer c2;
        public Pair(Integer c1, Integer c2) {
            this.c1 = c1;
            this.c2 = c2;
        }
        @Override
        public int hashCode() {
            int prime = 31, ret = 1;
            ret = ret*prime + c1.hashCode();
            ret = ret*prime + c2.hashCode();
            return ret;
        }
        @Override
        public boolean equals(Object obj) {
            if(obj instanceof Pair) {
                return c1.equals(((Pair) obj).c1) && c2.equals(((Pair) obj).c2);
            }
            return false;
        }
    }
    private static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    private static StringTokenizer tokenizer = new StringTokenizer("");
    private static String next() throws IOException{
        while(!tokenizer.hasMoreTokens()){tokenizer = new StringTokenizer(reader.readLine());}
        return tokenizer.nextToken();
    }
    public static int nextInt() throws IOException {return Integer.parseInt(next());}
    public static Long nextLong() throws IOException {return Long.parseLong(next());}
    public static double nextDouble() throws IOException {return Double.parseDouble(next());}
    public static char nextChar() throws IOException {return next().toCharArray()[0];}
    public static String nextString() throws IOException {return next();}
    public static String nextLine() throws IOException {return reader.readLine();}
}

Solution 2 (runtime: 968 ms):
//package Practice;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.*;

public class AdrenalineRush {
    public static void swap(int[] arr, int l) {
        int temp = arr[l];
        arr[l] = arr[l+1];
        arr[l+1] = temp;
    }
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out);
        int n = Integer.parseInt(br.readLine());
        int[] arr = new int[n];
        StringTokenizer st = new StringTokenizer(br.readLine());
        HashMap<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++) {
            arr[i] = Integer.parseInt(st.nextToken());
            map.put(arr[i], i);
         }
        if (n == 1) {
            pw.println("0");
            pw.close();
            return;
        }
        HashMap<Integer, Integer> map2 = new HashMap<>();
        int[] arr2 = new int[n];
        for (int i = 0; i < n; i++) {
            arr2[i] = i+1;
            map2.put(i+1, i);
        }
        ArrayList<String> moves= new ArrayList<>();
        for (int i = n-1; i >= 0; i--) {
            int curNum = arr[i];
            int startIdx = map2.get(curNum);
            int endIdx = map.get(curNum);
            // pass everything that starts in front
           // System.out.println("starting passing phase, arr2 is " + Arrays.toString(arr2) + " and curNum is " + curNum + " and start: " + startIdx);
            for (int j = startIdx-1; j >= 0; j--) {
                moves.add(arr2[j+1] + " " +  arr2[j]);
                swap(arr2, j);
                //System.out.println("passed 1, move was " + moves.getLast());
            }
            for (int j = 0; j < startIdx; j++) {
                map2.put(arr2[j], j);
            }
            startIdx = map2.get(curNum);
            // then get passed by everything that ends in front
            //System.out.println("at i="+i+", curNum is " + curNum + " and start:" + startIdx + " and end:" + endIdx);
            if (startIdx < endIdx) {
                //System.out.println("starting going back phase");
                while (startIdx < endIdx) {
                    //System.out.println("one move with num = " + curNum);
                    moves.add(arr2[startIdx+1] + " " + arr2[startIdx]);
                    int temp = arr2[startIdx];
                    map2.put(arr2[startIdx], map2.get(arr2[startIdx]) + 1);
                    map2.put(arr2[startIdx+1], map2.get(arr2[startIdx+1]) - 1);
                    arr2[startIdx] = arr2[startIdx+1];
                    arr2[startIdx+1] = temp;
                    startIdx++;
            //        pw.println("arr2:" + Arrays.toString(arr2) + " and last move was " + moves.getLast());
                }
            }
            for (int j = 0; j < startIdx; j++) {
                map2.put(arr2[j], j);
            }
          //  System.out.println("arr2 at the end of the process:" + Arrays.toString(arr2));
        }
        //System.out.println("arr2:" + Arrays.toString(arr2));
        /*HashSet<String> moveSet = new HashSet<>();
        moveSet.addAll(moves);
        for (int i = 0; i < n - 1; i++) {
            if (!moveSet.contains(arr2[i] + " " + arr2[i+1]) && !moveSet.contains(arr2[i+1] + " " + arr2[i])) {
                moves.add(arr2[i+1] + " " + arr2[i]);
                moves.add(arr2[i] + " " + arr2[i+1]);
            }
        }*/
        pw.println(moves.size());
        for (String move: moves) {
            pw.println(move);
        }
        // do extra stuff

        pw.close();
        br.close();
    }
}