问题 单项选择题

对于长度为n的线性表,在最坏情况下,下列各排序法所对应的比较次数中正确的是(  )。

A.冒泡排序为n(n-1)/2

B.简单插入排序为n

C.希尔排序为n

D.快速排序为n/2

答案

参考答案:A

解析:【解析】在最坏情况下,冒泡排序所需要的比较次数为n(n-1)/2;简单插入排序所需要的比较次数为n(n-I)/2;希尔排序所需要的比较次数为0(nl’5);堆排序所需要的比较次数为O(nl092n)。

单项选择题
阅读理解

开放性阅读。

     The power of nature Wind, water, fire and ice-these powerful natural forces shaped the land of America

in the past. They are still changing it today.

     The Colorado River slowly cut through stone to make the Grand Canyon.

     Long ago, ice sheets cut Yosemite Valley and glaciers (冰川) were moving in Alaska.

     Rains and storms hit the land from time to time. Fires sometimes burn down forests and destroy the homes

of wide animals. This happened in Yellowstone Park in 1998.

     Dead volcanic (火山的) mountains such as Haleakala on Moui and Crater Lake in Oregon are beautiful to

look at. There are also several active volcanoes in the US, especially along the Pacific Coast. There are also

many earthquakes in this area. Scientists can do nothing to control earthquakes or volcanoes. This was shown

clearly on May 18, 1980. At 8: 32 that morning, Mount St. Helens in Washington State erupted (爆发). The top

of the mountain was blown off.

     Over 60 people-campers, scientists, journalists, and forest workers were killed. Hundreds of square miles

of forests were knocked down. In towns over 100 miles away, day suddenly became night. An ash cloud hid

the sun for many hours. Town and fields in Washington, Oregon, and Idaho were covered with dirty grey ash.

     Scientists knew that Mount St. Helens could erupt soon but no one could say when. And no one expected

the terrible strength of the eruption. Many people were surprised and weren't ready. Harry R. Truman, 84,

owned a small hotel in Mount St. Helens. Scientists had asked him to leave because the volcano was becoming

dangerous.

     Harry Truman would not leave his home. Now it is covered with many feet of dirty ash. A small cross

stands above the place where Harry probably died. Perhaps it is better that he did not see what happened to

Mount St Helens, the once beautiful lake, and the forests.

     But slowly, life is returning to the dead area around the mountain. Grass and small plant are beginning to

grow again. Deer and birds have been seen in the area. The land will never be the same as it once was. Perhaps

Mount St. Helens will erupt again but this is all part of nature's pattern of change, and man has little power to

control it. 

根据短文内容,判断下列各句的正(T)误(F)。

( )1. The Colorado River slowly cut through stone to make the Grand Canyon.

( )2. Long ago, ice sheets made Yosemite Valley and the Great Lakes, and glaciers are not moving in Alaska.

( )3. Scientists knew exactly when Mount St. Helens would erupt.

( )4. Harry was finally persuaded to leave his home.

( )5. Now the land is not the same as it once was.