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前间壁心梗心电图改变出现在（）
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试编写算法判断两棵二叉树是否等价。若二叉树T1和T2等价，则T1和T2都是空的二叉树，或T1和T2的根结点的值相同，并且T1的左子树与T2的左子树是等价的，T1的右子树与T2的右子树是等价的。
以下程序段的时间复杂度为______。 for(i=0；i＜n；i++) for(j=0；j＜m；j++) A[i][j]=0；
Last month, Hansen Transmissions International, a maker of gearboxes for wind turbines, was listed on the London Stock Exchange. Nothing noteworthy about that, you might say, despite the jump in the share price on the first day of trading and the handsome gain since: green technology is all the rage, is it not But Hansen exemplifies another trend too, which should prove every bit as durable: the rise of multinational companies from emerging economies. Its parent is Suzlon, an Indian firm that began life as a textile manufacturer but is now among the world’s five leading makers of wind turbines. Along the way, Suzlon has acquired not only Hansen, originally Belgian, but also REpower, a German wind-energy firm, spending over $ 2 billion on the pair. The world is now replete with Suzlons: global companies from emerging economies buying businesses in rich countries as well as in poorer places. Another Indian company, Tata Motors, looks likely to add to the list soon, by buying two grand old names of British carmaking, Jaguar and Land Rover, from America’s enfeebled Ford. As a symbol of a shift in economic power, this is hard to match Economic theory says that this should not happen. Richer countries should export capital to poorer ones, not the other way round. Economists have had to get used to seeing this turned on its head in recent years, as rich countries have run large current-account deficits and borrowed from China and other emerging economies (notably oil, exporters) with huge surpluses. Similarly, foreign direct investment (FDI) the buying of companies and the building of factories and offices abroad— should also flow from rich to poor, and with it managerial and entrepreneurial prowess. It is not yet time to tear up the textbook on FDI. According to the UN Conference on Trade and Development (UNCTAD), in 2006 the flow of FDI into developing economies exceeded the outflow by more than $ 200 billion. But the transfer of finance and expertise is by no means all in one direction. Developing economies accounted for one-seventh of FDI outflows in 2006, most of it in the form of takeovers. Indian companies have done most to catch the eye, but firms from Brazil, China and Mexico, in industries from cement to consumer electronics and aircraft manufacture, have also gone global. Up to a point, emerging-market multinationals have been buying Western know-how. But they have been bringing managerial and entrepreneurial skill, as well as just money, to the companies they buy. British managers bear grudging witness to the financial flair of Mexican cement bosses; Boeing and Airbus may have learnt a thing or two from the global supply chains of Brazil’s Embraer. Perhaps no one should be surprised. Half a century ago, Japan was a poor country, today Sony and Toyota are among the best-known and mightiest companies on the planet. South Korea and Taiwan are still listed as developing countries in UNCTAD’s tables, but that seems bizarrely outdated for the homes of Samsung and Taiwan Semiconductor. Now another generation is forming. To its critics, globalization may be little more than a license for giant Western companies to colonize the emerging world, yet more arid more firms from poorer economies are planting their flags in rich ground. Alas, further liberalization is not certain. The Doha round of global trade talks has been bogged down, partly in squabbles about farm trade but also over industrial tariffs in the emerging world. The services negotiations are half-hearted and direct talks on FDI were ruled out long ago, largely because of developing countries’ fears about rich invaders. And the gains forgone are considerable, a new book by the World Bank estimates that reforming services in developing countries could raise their growth rates by a percentage point. Were OECD countries to allow temporary immigration of skilled workers in service industries, the global gains might exceed $ 45 billion. A few emerging-market giants—notably India’s software firms—have been prepared to stand up for liberalization. But most have not made their voices heard. How sad for free trade, such companies would provide much better illustrations of the success of globalization than the familiar Western names do (unless you think Coca-colonization sounds really cool). And how short-sighted of them. Even if some of these adolescents grew up behind tariff barriers, that represents their past: their future will surely lie in global markets. If the Doha round fails, the next opportunity may be a long time coming. What is the author’s attitude towards those firms which haven’t been prepared for liberalization
The toughest patches on Chicago’s South side offer few havens for children. Outside are flying bullets and police sirens; inside are poor teenage mothers and’ (occasionally) fathers. Yet here, in the shadow of a condemned public-housing block, a cluster of pastel-colored buildings contains what many experts see as a model for early childhood education in America. The Educate Centre, run by a non-profit group called the Ounce of Prevention Fund, offers an unusual mixture of care and education to 153 black children, from six weeks to five years old, who have little other stability in their lives. The benefits of early education are well known. It helps to determine how long children stay in high school, whether they turn to crime, and how quickly they will find a job. A study by the National Institute for Early Education Research says that every dollar invested in good, full-day, year-round pre-school education (which is rare) yields a $ 4 return in the long run to children, their families and taxpayers. "There’s a huge cost-benefit advantage just in decreased jail time," says James Heckman, an economist at the University of Chicago. With state budget so tight, pre-school programmes are suddenly vulnerable. New York state, for one, is threatening to cut universal pre-school education, and programmes are threatened in Tennessee and Massachusetts, among others. Ten states cut pre-school funding in 2002. A few states hope to make progress, though: the governor of Illinois wants to set up a programme for poor children deemed at risk. He hopes it will grow, over three years, to cover 25,000 children at a cost of $ 90, though a huge state budget deficit may squash his plans. Congress is now considering reauthorization of the Head Start programme, which provides educational, nutritional, medical and social services to the poor three and four year olds, and their families. The Bush administration is proposing changes—improvements, it says—that will shift accountability for Head Start to the states, where the money is spent. But the public-funded pre- kindergarten programmes now available in 40-odd states vary greatly in quality and in the numbers they serve. Some early-schooling advocates worry, therefore, that a shift of Head Start to the grates will undermine national standards. They also fear that cash-strapped states will cut back other pre-school programmes further if they gain control over Head Start, or that money will no longer he earmarked for extra food and health checks. "If kids are hungry or can’t see, they’re never going to learn," says Harriet Meyer, the president of the Ounce of Prevention Fund. The future of Early Head Start, which serves children from birth to three, is equally uncertain. Head Start currently provides about $7,000 for each child, and Early Head Start provides $8,000-10,000. The Educare Centre spends an average of $13,000 for each child by combining Head Start and Early Head Start cash with state money for other programmes. Compared with the hodgepodge of pre-school activities that millions of American parents cobble together, the Educare Centre is admirably integrated. By pooling money from different sources, it can hire plenty of educated teachers and pay them well; it takes children for a full day, all year round; providing a safe and cheerful place in which to play and learn Why are there not more such places The reasons include turf squabbles and jealousy among other child-care groups, unwillingness to believe that existing programmes need improving, bureaucratic hassles over families’ eligibility for funding, and lack of money. Researeh also shows that many Americans think pre-school children should be at home with their mothers. But that is a vanished age. Nowadays, when 73% of American mothers work, including 61% who have children under three, efficient and affordable child care is essential for employee-productivity as well as for the good of the children themselves. Adele Simmons, of Metropolis 2020 in Chicago, says it is time to invest in children as part of the nation’s social infrastructure. "The increase in funding for roads and bridges has been far greater than the increase in funding for kids," she says. "Kids who enter school not ready to learn never catch up. \ What is the author’s main purpose of writing this article
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