本文介绍了为什么插入排序总是跳动在此实现归并排序?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我不明白:为什么我插入排序实施殴打,每次归并排序,任何规模的 N
有关? 公开名单<的Int32> InsertionSort(名单<的Int32>元素,布尔升=真) { 对于(的Int32 J = 1; J< elements.Count; J ++) { INT32键=因素[J]。 INT32 I =的J - 1; 而(ⅰ> = 0&安培;及(元素[I] .CompareTo(键)大于0)==升序) 元素[I + 1] =元素[我 - ]。 元素[I + 1] =键; } 返回元素; }公开名单<的Int32>归并(名单<的Int32>元素,布尔升=真) { 排序(元素,0,elements.Count - 1); 返回元素; } 私人无效归并(名单<的Int32>元素的Int32在startIndex,的Int32计数) { 如果(在startIndex<计数) { INT32一半=(在startIndex +计数).Divide(2 RoundMethod.Floor); 排序(元素,在startIndex一半); 排序(元素,半数+ 1,计数); 合并(元素,在startIndex,一半,算); } } 公开名单<的Int32>合并(名单<的Int32>元素的Int32下界,的Int32一半的Int32上界) { 的Int32 I = 0; 的Int32 J = 0; INT32 lowerElementsCount =半 - 下界+ 1; INT32 upperElementsCount =上界 - 半; 名单<的Int32>左=新的名单,其中,的Int32>(); 而(I< lowerElementsCount) left.Add(元素[下界+ I +]); 名单<的Int32>右=新的名单,其中,的Int32>(); 而(J< upperElementsCount) right.Add(元素[半数+ J + + + 1]); left.Add(Int32.MaxValue); right.Add(Int32.MaxValue); I = 0; J = 0; 对于(INT K =下界; K< =上界; k ++) 如果(左[1] - =右[J]。) { 元素[K] =左[I] 我++; } 其他 { 元素[K] =右[J]。 J ++; } 返回元素; }
下面是我的结果:
分拣1个元素 合并排序:花费时间:0毫秒(1513蜱) 插入排序:花费时间:0毫秒(1247蜱) 分拣10种元素 合并排序:花费时间:1毫秒(2710蜱) 插入排序:花费时间:0毫秒(3蜱) 分拣100个元素 合并排序:花费时间:0毫秒(273蜱) 插入排序:花费时间:0毫秒(11刻度) 分拣1000个元素 合并排序:花费时间:1毫秒(3142蜱) 插入排序:花费时间:0毫秒(72刻度) 分拣10000元素 合并排序:执行时间:18毫秒(30491蜱) 插入排序:花费时间:0毫秒(882蜱)
而code来进行测试:
静态无效的主要(字串[] args) { 的for(int i = 1; I< 100000; I * = 10) { 名单<的Int32>元素= GetFilledList(I,0,Int32.MaxValue,假); Console.WriteLine(排序{0}元素,elements.Count); 秒表SW =新的秒表(); //合并排序 sw.Start(); 新归并()排序(元素)。 sw.Stop(); Console.WriteLine(合并排序:花费时间:{0}毫秒({1}蜱),sw.ElapsedMilliseconds,sw.ElapsedTicks); //插入排序 sw.Restart(); 新InsertionSort()排序(元素)。 sw.Stop(); Console.WriteLine(插入分页:花费时间:{0}毫秒({1}蜱),sw.ElapsedMilliseconds,sw.ElapsedTicks); Console.WriteLine(); } Console.ReadKey(); }在万一有人想知道我是从算法导论这些算法,托马斯H Cormen(作者)查尔斯E. Leiserson(作者),罗纳德·L.维斯特(作者),克利福德·斯坦(作者)
编辑:
静态列表<的Int32> GetFilledList(的Int32量的Int32下界,的Int32上界,布尔mayRepeat =真) { 名单<的Int32>数=新的名单,其中,的Int32>(); 随机R =新的随机(); 的for(int i = 0; I<数量;我++) { INT32 NUMERO = r.Next(下界,上界); 而(mayRepeat&安培;!&安培; numbers.Contains(NUMERO)) NUMERO = r.Next(下界,上界); numbers.Add(NUMERO); } 返回的数字; }解决方案
因为,合并排序后,在元素中的对象已经排序。做的是另
元素= GetFilledList(I,0,Int32.MaxValue,假);
在
sw.Restart();I don't understand: why is my insertion sort implementation beating merge sort every time, for any size of n?
public List<Int32> InsertionSort(List<Int32> elements, Boolean ascending = true) { for (Int32 j = 1; j < elements.Count; j++) { Int32 key = elements[j]; Int32 i = j - 1; while (i >= 0 && (elements[i].CompareTo(key) > 0) == ascending) elements[i + 1] = elements[i--]; elements[i + 1] = key; } return elements; }public List<Int32> MergeSort(List<Int32> elements, Boolean ascending = true) { Sort(elements, 0, elements.Count - 1); return elements; } private void MergeSort(List<Int32> elements, Int32 startIndex, Int32 count) { if(startIndex < count) { Int32 half = (startIndex + count).Divide(2, RoundMethod.Floor); Sort(elements, startIndex, half); Sort(elements, half + 1, count); Merge(elements, startIndex, half, count); } } public List<Int32> Merge(List<Int32> elements, Int32 lowerBound, Int32 half, Int32 upperBound) { Int32 i = 0; Int32 j = 0; Int32 lowerElementsCount = half - lowerBound + 1; Int32 upperElementsCount = upperBound - half; List<Int32> left = new List<Int32>(); while (i < lowerElementsCount) left.Add(elements[lowerBound + i++]); List<Int32> right = new List<Int32>(); while (j < upperElementsCount) right.Add(elements[half + j++ + 1]); left.Add(Int32.MaxValue); right.Add(Int32.MaxValue); i = 0; j = 0; for (int k = lowerBound; k <= upperBound; k++) if (left[i] <= right[j]) { elements[k] = left[i]; i++; } else { elements[k] = right[j]; j++; } return elements; }
Here are my results:
SORTING 1 ELEMENTS MERGE-SORT: TIME SPENT: 0ms (1513 ticks) INSERTION-SORT: TIME SPENT: 0ms (1247 ticks) SORTING 10 ELEMENTS MERGE-SORT: TIME SPENT: 1ms (2710 ticks) INSERTION-SORT: TIME SPENT: 0ms (3 ticks) SORTING 100 ELEMENTS MERGE-SORT: TIME SPENT: 0ms (273 ticks) INSERTION-SORT: TIME SPENT: 0ms (11 ticks) SORTING 1000 ELEMENTS MERGE-SORT: TIME SPENT: 1ms (3142 ticks) INSERTION-SORT: TIME SPENT: 0ms (72 ticks) SORTING 10000 ELEMENTS MERGE-SORT: TIME SPENT: 18ms (30491 ticks) INSERTION-SORT: TIME SPENT: 0ms (882 ticks)
And the code for testing:
static void Main(string[] args) { for (int i = 1; i < 100000; i*=10) { List<Int32> elements = GetFilledList(i, 0, Int32.MaxValue, false); Console.WriteLine("SORTING {0} ELEMENTS", elements.Count); Stopwatch sw = new Stopwatch(); //MERGE SORT sw.Start(); new MergeSort().Sort(elements); sw.Stop(); Console.WriteLine("MERGE-SORT: TIME SPENT: {0}ms ({1} ticks)", sw.ElapsedMilliseconds, sw.ElapsedTicks); //INSERTION SORT sw.Restart(); new InsertionSort().Sort(elements); sw.Stop(); Console.WriteLine("INSERTION-SORT: TIME SPENT: {0}ms ({1} ticks)", sw.ElapsedMilliseconds, sw.ElapsedTicks); Console.WriteLine(); } Console.ReadKey(); }In case anyone wondering I got these algorithms from Introduction to Algorithms, Thomas H. Cormen (Author), Charles E. Leiserson (Author), Ronald L. Rivest (Author), Clifford Stein (Author)
EDIT:
static List<Int32> GetFilledList(Int32 quantity, Int32 lowerBound, Int32 upperBound, Boolean mayRepeat = true) { List<Int32> numbers = new List<Int32>(); Random r = new Random(); for (int i = 0; i < quantity; i++) { Int32 numero = r.Next(lowerBound, upperBound); while(!mayRepeat && numbers.Contains(numero)) numero = r.Next(lowerBound, upperBound); numbers.Add(numero); } return numbers; }解决方案
because, after the merge sort, the objects in elements are already sorted. do another
elements = GetFilledList(i, 0, Int32.MaxValue, false);before the
sw.Restart();
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为什么插入排序总是跳动在此实现归并排序?
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