885. Spiral Matrix III

 JAVA

• class Solution {
      public int[][] spiralMatrixIII(int rows, int cols, int rStart, int cStart) {
          int cnt = rows * cols;
          int[][] ans = new int[cnt][2];
          ans[0] = new int[] {rStart, cStart};
          if (cnt == 1) {
              return ans;
          }
          for (int k = 1, idx = 1;; k += 2) {
              int[][] dirs = new int[][] { {0, 1, k}, {1, 0, k}, {0, -1, k + 1}, {-1, 0, k + 1} };
              for (int[] dir : dirs) {
                  int r = dir[0], c = dir[1], dk = dir[2];
                  while (dk-- > 0) {
                      rStart += r;
                      cStart += c;
                      if (rStart >= 0 && rStart < rows && cStart >= 0 && cStart < cols) {
                          ans[idx++] = new int[] {rStart, cStart};
                          if (idx == cnt) {
                              return ans;
                          }
                      }
                  }
              }
          }
      }
  }

C++

• class Solution {
  public:
      vector<vector<int>> spiralMatrixIII(int rows, int cols, int rStart, int cStart) {
          int cnt = rows * cols;
          vector<vector<int>> ans;
          ans.push_back({rStart, cStart});
          if (cnt == 1) return ans;
          for (int k = 1;; k += 2) {
              vector<vector<int>> dirs = { {0, 1, k}, {1, 0, k}, {0, -1, k + 1}, {-1, 0, k + 1} };
              for (auto& dir : dirs) {
                  int r = dir[0], c = dir[1], dk = dir[2];
                  while (dk-- > 0) {
                      rStart += r;
                      cStart += c;
                      if (rStart >= 0 && rStart < rows && cStart >= 0 && cStart < cols) {
                          ans.push_back({rStart, cStart});
                          if (ans.size() == cnt) return ans;
                      }
                  }
              }
          }
      }
  };