K Swap -- 归并排序

K Swap

https://atcoder.jp/contests/abc254/tasks/abc254_c

 

思路

 

 

Code

#include <bits/stdc++.h>
#include <vector>
#include <algorithm>
#include <deque>
#include <queue>
#include <string>
#include <set>
using namespace std;

/*
https://atcoder.jp/contests/abc254/tasks/abc254_c
*/


vector<int> a(200004, 0);

map<int, vector<int>> groups;


int main() {
    int n, k;

    cin >> n >> k;

    for (int i = 1; i <= n; i++) {
        cin >> a[i];

        /*
        group indexed from 0 to k-1
        1  --> group 0
        2 --> group 1
        ...
        k --> group k-1
        k+1 --> group 0
        k+2 --> group 1
        ...
        */
        int group_index = (i - 1) % k;
        groups[group_index].push_back(a[i]);
    }

    for (int i = 0; i < k; i++) {
        vector<int> &one_group = groups[i];
        sort(one_group.begin(), one_group.end());
//
//        for (int j = 0; j < one_group.size(); j++) {
//            cout << one_group[j] << " " ;
//        }
//
//        cout << endl;
    }

    int prev = groups[0][0];
    for (int i = 2; i <= n; i++) {
        int group_num = (i - 1) % k;
        int column = (i - 1) / k;

        int now = groups[group_num][column];
        if (prev <= now) {
            prev = now;
            continue;
        } else {
            cout << "No" << endl;
            return 0;
        }
    }

    cout << "Yes" << endl;
    return 0;
}