0054.cpp

class Solution {
public:
  vector<int> spiralOrder(vector<vector<int>> &mat) {
    int top = 0, bottom = mat.size() - 1;
    int left = 0, right = mat[0].size() - 1;
    vector<int> v;
    while (top <= bottom && left <= right) {
      for (int i = left; i <= right; i++) {
        v.push_back(mat[top][i]);
      }
      top++;
      for (int i = top; i <= bottom; i++) {
        v.push_back(mat[i][right]);
      }
      right--;
      if (top <= bottom) {
        for (int i = right; i >= left; i--) {
          v.push_back(mat[bottom][i]);
        }
        bottom--;
      }
      if (left <= right) {
        for (int i = bottom; i >= top; i--) {
          v.push_back(mat[i][left]);
        }
        left++;
      }
    }
    return v;
  }
};