[Leetcode] Spiral Matrix

class Solution {
public:
vector<int> spiralOrder(vector<vector<int> > &mat) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
vector<int> res;

int r = mat.size();
if (r == 0) return res;

int c = mat[0].size();
if (c == 0) return res;

int bri = 0;
int bci = 0;

while (r > 0 && c > 0)
{
if (r == 1)
{
for (int i = bci; i < bci + c; ++i)
res.push_back(mat[bci][i]);
break;
}
else if (c == 1)
{
for (int i = bri; i < bri + r; ++i)
res.push_back(mat[i][bri]);
break;
}

// top
for (int i = bci; i < bci + c; ++i)
res.push_back(mat[bri][i]);
// right
for (int i = bri + 1; i < bri + r; ++i)
res.push_back(mat[i][bci + c - 1]);

for (int i = bci + c - 2; i >= bci; --i)
res.push_back(mat[bri + r - 1][i]);

for (int i = bri + r - 2; i > bri; --i)
res.push_back(mat[i][bci]);

r -= 2;
c -= 2;
bri++;
bci++;
}
return res;
}
};