交换后转置

将第1行和最后一行，第二行和倒数第二行,…, 互换
互换完再转置就得到答案

#include <iostream>
#include <vector>

using namespace std;

const int N = 110;

vector<vector<int>> a(N, vector<int>(N,0));
vector<vector<int>> b(N, vector<int>(N,0));


int main()
{
    int n, m; cin >> n >> m;
    for(int i = 1; i <= n; ++i) {
        for(int j = 1; j <= m; ++j) cin >> a[i][j];
    }

    for(int i = 1; i <= n / 2; ++i) {
        swap(a[i], a[n-i+1]);
    }

    for(int i = 1; i <= n; ++i) {
        for(int j = 1; j <= m; ++j) {
            b[j][i] = a[i][j];
        }
    }

    for(int i = 1; i <= m; ++i) {
        for(int j = 1; j <= n; ++j)
            cout << b[i][j] << " ";
        cout << endl;
    }

    return 0;
}