Sleepy Cow Sorting

Interview

Time limit2sMemory limit512 MB

Summary
Find the minimum number of moves to sort a permutation, where each move takes the front element and inserts it k positions later, and output the move sizes.
Level

Medium6 of 10

Topics
Array, Greedy, Sorting, Implementation
Solved
No attempts yet

Problem

Farmer John is attempting to sort his NN cows (1≤N≤1051 \leq N \leq 10^5), conveniently numbered 1…N1 \dots N, before they head out to the pastures for breakfast.

Currently, the cows are standing in a line in the order p_1,p_2,p_3,…,p_Np\_1, p\_2, p\_3, \dots, p\_N, and Farmer John is standing in front of cow p_1p\_1. He wants to reorder the cows so that they are in the order 1,2,3,…,N1, 2, 3, \dots, N, with cow 11 next to Farmer John.

Today the cows are a bit sleepy, so at any point in time the only cow who is paying attention to Farmer John's instructions is the cow directly facing Farmer John. In one time step, he can instruct this cow to move kk paces down the line, for any kk between 11 and N−1N-1 inclusive. The kk cows whom she passes will amble forward, making room for her to insert herself in the line after them.

For example, suppose that N=4N=4 and the cows start off in the following order:

FJ: 4, 3, 2, 1

The only cow paying attention to FJ is cow 44. If he instructs her to move 22 paces down the line, the order will subsequently look like this:

FJ: 3, 2, 4, 1

Now the only cow paying attention to FJ is cow 33, so in the second time step he may give cow 33 an instruction, and so forth until the cows are sorted.

Farmer John is eager to complete the sorting, so he can go back to the farmhouse for his own breakfast. Help him find a sequence of instructions that sorts the cows in the minimum number of time steps.

Input

The first line of input contains NN. The second line contains NN space-separated integers: p_1,p_2,p_3,…,p_Np\_1, p\_2, p\_3, \dots, p\_N, indicating the starting order of the cows.

Output

The first line should contain a single integer, KK, giving the minimum number of time steps required to sort the cows.

The second line should contain KK space-separated integers, c_1,c_2,…,c_Kc\_1, c\_2, \dots, c\_K, each in the range 1…N−11 \ldots N-1. Furthermore, if in the ii-th time step FJ instructs the cow facing him to move c_ic\_i paces down the line, then after KK time steps the cows should be in sorted order.

If there are multiple optimal instruction sequences, your program may output any of them.

Examples1

  1. Example 1

    Input
    4
    1 2 4 3
    
    Expected output
    3
    2 2 3