不确定是否算暴力解题

从最理想的正方形开始依次寻找；

        for (int length = Math.min(arr.length, arr[0].length); length > 1; length--) {
            for (int y = 0, y_length = arr.length; y < y_length - length + 1; y++) {
                for (int x = 0, x_length = arr[y].length; x < x_length - length + 1; x++) {
                    if (validate(length, arr, x, y)) {
                        System.out.println("size = " + length * length);
                        return;
                    }
                }
            }
        }
        System.out.println("size = 1");

接着是一个用来验证当前长度是否符合正方形要求的逻辑

    private static boolean validate(int length, int[][] arr, int x, int y){
        for (int i = y, i_l = y+length; i < i_l; i++) {
            for (int j = x, j_l = x+length; j < j_l; j++) {
                if (arr[i][j] != 1) return false;
            }
        }
        return true;
    }