题目：

题解：

func maximalRectangle(matrix [][]byte) (ans int) {
    if len(matrix) == 0 {
        return
    }
    m, n := len(matrix), len(matrix[0])
    left := make([][]int, m)
    for i, row := range matrix {
        left[i] = make([]int, n)
        for j, v := range row {
            if v == '0' {
                continue
            }
            if j == 0 {
                left[i][j] = 1
            } else {
                left[i][j] = left[i][j-1] + 1
            }
        }
    }
    for j := 0; j < n; j++ { // 对于每一列，使用基于柱状图的方法
        up := make([]int, m)
        down := make([]int, m)
        stk := []int{}
        for i, l := range left {
            for len(stk) > 0 && left[stk[len(stk)-1]][j] >= l[j] {
                stk = stk[:len(stk)-1]
            }
            up[i] = -1
            if len(stk) > 0 {
                up[i] = stk[len(stk)-1]
            }
            stk = append(stk, i)
        }
        stk = nil
        for i := m - 1; i >= 0; i-- {
            for len(stk) > 0 && left[stk[len(stk)-1]][j] >= left[i][j] {
                stk = stk[:len(stk)-1]
            }
            down[i] = m
            if len(stk) > 0 {
                down[i] = stk[len(stk)-1]
            }
            stk = append(stk, i)
        }
        for i, l := range left {
            height := down[i] - up[i] - 1
            area := height * l[j]
            ans = max(ans, area)
        }
    }
    return
}

func max(a, b int) int {
    if a > b {
        return a
    }
    return b
}