javascript学习6-练习之3二分查找算法

 1 //二分查找
 2 var string2=[1,3,42,88,123,143];
 3 var leftIndex=0;
 4 var rightIndex=5;
 5 function binarySearch(string2,findVal,leftIndex,rightIndex)
 6 {
 7     if(leftIndex>rightIndex)
 8     {
 9         //    提示找不到，防止无穷递归
10         document.write("找不到");
11         return;
12     }    
13     var midVal=string2[Math.floor((leftIndex+rightIndex)/2)]
14     //比较
15     if(findVal>midVal)
16     {
17         leftIndex=Math.floor((leftIndex+rightIndex)/2)+1;
18         binarySearch(string2,findVal,leftIndex,rightIndex);
19     }
20     else if(findVal<midVal)
21     {
22         rightIndex=Math.floor((leftIndex+rightIndex)/2)-1;
23         binarySearch(string2,findVal,leftIndex,rightIndex);
24     }
25     else if(findVal==midVal)
26     {
27         document.writeln("有这个数字，而且位置是"+Math.floor((leftIndex+rightIndex)/2));
28     }
29 }
30 binarySearch(string2,143,0,string2.length);