二分模板
class Solution {public static void main(String[] args) {int[] arr={1,2,2,2,2,4,5,6};int l=0,r=arr.length-1;while(l<r){int mid=l+(r-l)/2;if(arr[mid]>=2) r=mid;else l=mid+1;}System.out.println("l:"+l+"r:"+r);System.out.println("left: "+l);l=0;r=arr.length-1;while(l<r){int mid=l+(r-l+1)/2;if(arr[mid]<=2) l=mid;else r=mid-1;}System.out.println("l:"+l+"r:"+r);System.out.println("right: "+r);}
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