var maximalSquare = function(matrix) {

if (!matrix || !matrix.length || !matrix[0].length) return 0

let maxLen = 0

const m = matrix.length + 1

const n = matrix[0].length + 1

const dp = Array(m).fill(0).map(() => [0])

dp[0] = Array(n).fill(0)

for (let i = 1; i < m; i++) {

for (let j = 1; j < n; j++) {

if (matrix[i - 1][j - 1] === '1') {

dp[i][j] = Math.min(dp[i - 1][j], dp[i][j - 1], dp[i - 1][j - 1]) + 1

maxLen = Math.max(maxLen, dp[i][j])

} else {

dp[i][j] = 0

}

}

}

return maxLen * maxLen

};