Leetcode 59: Spiral Matrix II

leetcode_59.cpp

#include <iostream>
#include <vector>

using namespace std;

void addLayer(vector<vector<int>>& m, int layer) {
    int n = m.size();
    int val = 0; //last value
    if (layer > 0)
        val = m[layer][layer-1];

    for (int r=layer,c=layer; c<n-layer; ++c)  //fill right ->
        m[r][c] = ++val;
    for (int r=layer+1,c=n-1-layer; r<n-layer; ++r)  //fill down  v
        m[r][c] = ++val;
    for (int r=n-1-layer,c=n-1-1-layer; c>=0+layer; --c) //fill left <-
        m[r][c] = ++val;
    for (int r=n-1-1-layer,c=layer; r>layer; --r) //fill up ^
        m[r][c] = ++val;
}

vector<vector<int>> generateMatrix(int n) {
    if (n <= 0)
        return {};
    vector<vector<int>> m(n, vector<int>(n,0));
    int layers = (n+1)/2;

    for (int i=0; i<layers; ++i) 
        addLayer(m, i);
    return m;
}

void printv(const vector<vector<int>>& m) {
    for (int r=0; r<m.size(); ++r) {
        for (int c=0; c<m[r].size(); ++c)
            cout << (m[r][c]<10?" ":"") << m[r][c] << " ";
        cout << "\n";
    }
    cout << "\n";
}

int main() {
    auto m = generateMatrix(5);
    printv(m);

    return 0;
}