在排序数组中查找数字 I

二分找左右边界

class Solution {
    public int search(int[] nums, int target) {
        int start=findLeft(nums,target),end=findRight(nums,target);
        if(start==-1||end==-1) return 0;  
        return end-start+1;
    }

    public int findLeft(int[] nums, int target){
    int n=nums.length;
    int l=0,r=n-1;
    while(l<=r){
        int mid=l+(r-l)/2;
        if(nums[mid]>target){
            r=mid-1;
        }else if(nums[mid]<target){
            l=mid+1;
        }else{
            r=mid-1;
        }
    }
    if(l>=n||nums[l]!=target) return -1;
    return l;
    }
    public int findRight(int[] nums, int target){
    int n=nums.length;
    int l=0,r=n-1;
    while(l<=r){
        int mid=l+(r-l)/2;
        if(nums[mid]>target){
            r=mid-1;
        }else if(nums[mid]<target){
            l=mid+1;
        }else{
            l=mid+1;
        }
    }
    if(r<0||nums[r]!=target) return -1;
    return r;
    }
    
}