54.cpp

/**
 *    author:   vulkan
 *    created:  01.06.2020 04:55:50 PM
**/
#include <bits/stdc++.h>

using namespace std;

vector<int> spiralOrder(vector<vector<int>> &matrix) {
    int n = matrix.size();
    int m = (n > 0) ? matrix[0].size() : -1;
    if (m == -1 or m == 0) {
        return {};
    }

    vector<int> ans(n * m);
    int end_i = n / 2, end_j = m / 2;
    int u = 0, d = n - 1, l = 0, r = m - 1;
    int k = 0;
    while (k < n * m) {
        for (int i = l; i <= r; ++i) {
            ans[k++] = matrix[u][i];
        }
        u++;

        if (k == n * m) {
            break;
        }

        for (int i = u; i <= d; ++i) {
            ans[k++] = matrix[i][r];
        }
        r--;

        if (k == n * m) {
            break;
        }

        for (int i = r; i >= l; --i) {
            ans[k++] = matrix[d][i];
        }
        d--;

        if (k == n * m) {
            break;
        }

        for (int i = d; i >= u; --i) {
            ans[k++] = matrix[i][l];
        }
        l++;
    }

    return ans;
}

int main(int argc, char const *argv[]) {
    int n, m;
    cin >> n >> m;
    vector<vector<int>> matrix(n, vector<int>(m));
    for (int i = 0; i <= n - 1; ++i) {
        for (int j = 0; j <= m - 1; ++j) {
            cin >> matrix[i][j];
        }
    }

    vector<int> ans = spiralOrder(matrix);
    for (int x : ans) {
        cout << x << ' ';
    }

    return 0;
}