Search for a Range

public class Solution {
    public int[] searchRange(int[] A, int target) {
        int[] res = {-1, -1};
        if(A==null || A.length<1) return res;
        int ll = 0, lr = A.length-1, rl=0,rr = A.length-1;
        while(ll<=lr){
            int m = (ll+lr)/2;
            if(A[m]<target){
                ll=m+1;
            }else  
                lr= m-1;
        }
        while(rl<=rr){
            int m = (rl+rr)/2;
            if(A[m]<=target){// 如果是< 就错了，因为rr的位置和ll一样，必然不可以是等于的情况
                rl=m+1;
            }else  
                rr= m-1;
        }
        if(ll<=rr){
            res[0] = ll;
            res[1] = rr;
        }
        return res;
    }
}

二分法和夹逼法

ref

http://blog.csdn.net/linhuanmars/article/details/20593391