二分查找

1）遞歸

 1             function binarySearch(data, dest, start, end){  
 2                 var end = end || data.length - 1,  
 3                     start = start || 0,  
 4                     m = Math.floor((start + end) / 2);  
 5                 if(data[m] == dest){  
 6                     return m;  
 7                 }  
 8                 if(dest < data[m]){  
 9                     return binarySearch(data, dest, 0, m-1);  
10                 }else{  
11                     return binarySearch(data, dest, m+1, end);  
12                 }
13                 return false;  
14             }
15             var arr = [-34, 1, 3, 4, 5, 8, 34, 45, 65, 87];  
16             binarySearch(arr,4);  
17             //3

2）非遞歸

 1              function binarySearch(data, dest){  
 2                 var h = data.length - 1,  
 3                     l = 0;  
 4                 while(l <= h){  
 5                     var m = Math.floor((h + l) / 2);  
 6                     if(data[m] == dest){  
 7                         return m;  
 8                     }  
 9                     if(dest > data[m]){  
10                         l = m + 1;  
11                     }else{  
12                         h = m - 1;  
13                     }  
14                 }  
15                 
16                 return false;  
17             }  
18             var arr = [-34, 1, 3, 4, 5, 8, 34, 45, 65, 87];  
19             binarySearch(arr,4);  
20             //3