二分查找（非递归）

public class Demo{

    public static int binarySearch(int[] arr,int target){
        int left = 0;
        int right = arr.length-1;
        while(left<=right){
            int mid = (left+right)/2;
            if(arr[mid]==target){
                return mid;
            }else if(arr[mid]>target){
                right = mid-1;// 向左查
            }else{
                left = mid+1;// 向右查
            }
        }
    }
    
}
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