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64. Minimum Path Sum 👍

  • Time: $O(mn)$
  • Space: $O(1)$
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class Solution {
 public:
  int minPathSum(vector<vector<int>>& grid) {
    const int m = grid.size();
    const int n = grid[0].size();

    for (int i = 0; i < m; ++i)
      for (int j = 0; j < n; ++j)
        if (i > 0 && j > 0)
          grid[i][j] += min(grid[i - 1][j], grid[i][j - 1]);
        else if (i > 0)
          grid[i][0] += grid[i - 1][0];
        else if (j > 0)
          grid[0][j] += grid[0][j - 1];

    return grid[m - 1][n - 1];
  }
};

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class Solution {
  public int minPathSum(int[][] grid) {
    final int m = grid.length;
    final int n = grid[0].length;

    for (int i = 0; i < m; ++i)
      for (int j = 0; j < n; ++j)
        if (i > 0 && j > 0)
          grid[i][j] += Math.min(grid[i - 1][j], grid[i][j - 1]);
        else if (i > 0)
          grid[i][0] += grid[i - 1][0];
        else if (j > 0)
          grid[0][j] += grid[0][j - 1];

    return grid[m - 1][n - 1];
  }
}

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class Solution:
  def minPathSum(self, grid: list[list[int]]) -> int:
    m = len(grid)
    n = len(grid[0])

    for i in range(m):
      for j in range(n):
        if i > 0 and j > 0:
          grid[i][j] += min(grid[i - 1][j], grid[i][j - 1])
        elif i > 0:
          grid[i][0] += grid[i - 1][0]
        elif j > 0:
          grid[0][j] += grid[0][j - 1]

    return grid[m - 1][n - 1]