//对于一个从小到大的有序数列，返回查找值的索引(数组下标)

//二分查找，非递归方法

function BinSearch(arr, item){

    var left = 0;

    var right = arr.length-1;

    while(left<=right){

        var mid = Math.floor((left+right)/2);

          if(item == arr[mid]){

            return mid;

          }else if(item > arr[mid]){

            left = mid + 1;

          }else{

            right = mid - 1;

          }

    }

    return false;

}

var arr=[-34, 1, 3, 4, 5, 8, 34, 45, 65, 87];

console.log(BinSearch(arr,5));   //

//二分查找，递归方法

function BinSearch2(arr,item,left,right){

    var left = left || 0;

    var right = right || arr.length-1;

    var mid = Math.floor((left+right)/2);

    if(item == arr[mid]){

        return mid;

    }else if(item > arr[mid]){

        return BinSearch2(arr,item,mid+1,right);

    }else{

        return BinSearch2(arr,item,left,mid-1);

    }

    return false;

}

var arr1=[-34, 1, 3, 4, 5, 8, 34, 45, 65, 87];

console.log(BinSearch2(arr1,5));  //