[Javase] Array (Lookup-two-point lookup)

The precondition array must be ordered

Defines the minimum, maximum, and median index of a corner label

        int Min,max,mid;        Min=0;        Max=arr.length-1;        Mid= (Min+max)/2;

The above index needs to change, using a loop, condition: When the middle value is not equal to the target value

        int Min,max,mid;        Min=0;        Max=arr.length-1;        Mid= (Min+max)/2;          while (arr[mid]!=key) {            if(key<Arr[mid]) {                            }Elseif (arr[mid]<key) {                            }        }

When the median value is greater than the target value, the maximum angle is moved to the Middle corner label -1 position

When the median value is less than the target value, the minimum angle is moved to the Middle corner label +1 position

The middle angle Mark continues the two points

        int Min,max,mid;        Min=0;        Max=arr.length-1;        Mid= (Min+max)/2;          while (arr[mid]!=key) {            if(key<Arr[mid]) {                max=mid-1;            } Else if (arr[mid]<key) {                min=mid+1;            }            Mid= (Min+max)/2;        }         return mid;

There is a problem with the code at this point, when the target is not found, it will fall into a dead loop, plus a judgment

If not found, the minimum angle and the maximum angle bidding clubs dislocation

        intMin,max,mid; Min=0; Max=arr.length-1; Mid= (Min+max)/2;  while(arr[mid]!=key) {            if(key<Arr[mid]) {Max=mid-1; }Else if(arr[mid]<key) {min=mid+1; }            if(Min>max)return-1; Mid= (Min+max)/2; }        returnMid

Java Edition:

 Public classArraydemo {/**     * @paramargs*/     Public Static voidMain (string[] args) {int[] arr=New int[]{1,4,6,7,8,9}; System.out.println ("Index:" +keysearch (arr,7));//Index: 3System.out.println ("Index:" +helfsearch (arr,7));//Index: 3    }    /*** Two-point search *@paramarr *@paramKey *@return     */     Public Static intHelfsearch (int[] arr,intkey) {        intMin,max,mid; Min=0; Max=arr.length-1; Mid= (Min+max)/2;  while(arr[mid]!=key) {            if(key<Arr[mid]) {Max=mid-1; }Else if(arr[mid]<key) {min=mid+1; }            if(Min>max)return-1; Mid= (Min+max)/2; }        returnmid; }    /*** Gets the position where the value first appears in the array *@paramarr *@paramnum *@return     */     Public Static intKeysearch (int[] arr,intnum) {         for(inti=0;i<arr.length;i++){            if(arr[i]==num) {                returni; }        }        return-1; }}

PHP Version:

<?PHPclassarraydemo{ Public Static functionMain () {$arr=Array(1,4,6,7,8,9); Echo"Index:". Arraydemo::keysearch ($arr, 7);//Index: 3        Echo"Index:". Arraydemo::helfsearch ($arr, 7);//Index: 3    }    /** binary search * @param arr * @param key * @return*/     Public Static functionHelfsearch ($arr,$key){        $min=0; $max=Count($arr)-1; $mid=Ceil(($min+$max)/2);  while($arr[$mid]!=$key){            if($key<$arr[$mid]){                $max=$mid-1; }Else if($arr[$mid]<$key){                $min=$mid+1; }            $mid=Ceil(($min+$max)/2); if($min>$max)return-1; }        return $mid; }    /** * Gets the position where the value first appears in the array * @param arr * @param num * @return*/     Public Static functionKeysearch ($arr,$key){         for($i= 0;$i<Count($arr);$i++){            if($arr[$i]==$key){                return $i; }        }        return-1; }}arraydemo:: Main ();

[Javase] Array (Lookup-two-point lookup)