01-matrix.ts

export const updateMatrix = function (matrix: number[][]): number[][] {
  if (matrix.length === 0) return []

  const m = matrix.length
  const n = matrix[0].length

  // 左上 -> 右下
  for (let i = 0; i < m; i++) {
    for (let j = 0; j < n; j++) {
      if (matrix[i][j] !== 0) {
        matrix[i][j] = m + n
        if (i > 0) matrix[i][j] = Math.min(matrix[i - 1][j] + 1, matrix[i][j])
        if (j > 0) matrix[i][j] = Math.min(matrix[i][j - 1] + 1, matrix[i][j])
      }
    }
  }

  // 右下 -> 左上
  for (let i = m - 1; i >= 0; i--) {
    for (let j = n - 1; j >= 0; j--) {
      // distance
      if (matrix[i][j] !== 0) {
        if (j < n - 1) matrix[i][j] = Math.min(matrix[i][j], matrix[i][j + 1] + 1)
        if (i < matrix.length - 1) matrix[i][j] = Math.min(matrix[i][j], matrix[i + 1][j] + 1)
      }
    }
  }

  return matrix
}