静态查找
2011-01-20 16:29 Clingingboy 阅读(404) 评论(0) 编辑 收藏 举报
一.顺序查找
就从头到尾或者从尾到头
class DataFinder { static void Main() { var ints = new int[] {1, 2, 3, 6, 5, 4}; var result1 = FindFromHead(ints, 5); Console.WriteLine(result1); var result2 = FindFromEnd(ints, 5); Console.WriteLine(result2); } public static int FindFromHead(int[] ints, int key) { int step = 0; for (int i = 0; i < ints.Length - 1; i++) { step++; if (ints[i] == key) { Console.WriteLine("Head step:" + step); return key; } } return -1; } public static int FindFromEnd(int[] ints,int key) { int step = 0; for (int i = ints.Length-1; i >0;i--) { step++; if (ints[i] == key) { Console.WriteLine("End step:" + step); return key; } } return -1; } }
结果
二.折半查找(二分查找)
首先必须是有序的
public static int BinarySearch(int[] ints,int key) { //don't care //1,2,3,4,5,6 Array.Sort(ints); int step = 0; int low = 0, high = ints.Length - 1; int mid = 0; while (low<high) { step++; mid = (low + high) / 2; if (ints[mid] == key) { Console.WriteLine("BinarySearch step:" + step); return key; } if (ints[mid] > key) high = mid - 1; else low = mid + 1; } return -1; }
此图更详细
分块查找(索引顺序查找)
即将数据分块,比如将1-100,分成10块,分别存储1-10,2-20…91-100.那么查找81就可以直接从第8个块开始查找.
即通过一个辅助的数组存储数组的最大索引值,先通过索引值找到块,然后根据块开始查找.
public static int BlockSearch(int key) { //int var ints=new int[100]; var blocks = new Block[10]; for (int i = 1; i < 101; i++) { if (i%10 == 0) blocks[i / 10 - 1] = new Block() { Index = i - 10, Value = i }; ints[i - 1] = i; } int step = 0; //find Block Index First int index = 0; //21 for (int i = 0; i < blocks.Length; i++) { step++; if (key <= blocks[i].Value) { index = blocks[i].Index; break; } } //search key from block for (int i = index; i < index+blocks.Length-1; i++) { step++; if (ints[i] == key) { Console.WriteLine("BlockSearch setp:"+step); return key; } } return -1; }
查找91的结果