最大正方形

var maximalSquare = function (matrix) {
 let maxSide = 0;
  if (!matrix?.length || !matrix[0]?.length) {
    return maxSide;
  }
  const rows = matrix.length;
  const columns = matrix[0].length;
  const dp = new Array(rows)
  for (let i = 0; i < rows; i++) {
    dp[i] = new Array(columns).fill(0)
  }
  for (let i = 0; i < rows; i++) {
      for (let j = 0; j < columns; j++) {
          if (matrix[i][j] === '1') {
              if (i === 0 || j === 0) {
                  dp[i][j] = 1;
              } else {
                  dp[i][j] = Math.min(Math.min(dp[i - 1][j], dp[i][j - 1]), dp[i - 1][j - 1]) + 1;
              }
              maxSide = Math.max(maxSide, dp[i][j]);
          }
      }
  }
  return maxSide * maxSide;
};