二分查找
1， 右邊區(qū)間有序
1.1 target落在右邊，在右邊繼續(xù)二分
1.2 target落在左邊，在左邊二分

2，左邊有序
2.1 target落在左邊，在左邊繼續(xù)二分
2.2 target落在右邊，在左邊右分

找到就返回，沒找到的話在循環(huán)返回的l ,r中查找是否存在target.

int search(int* nums, int numsSize, int target) {
    int l = 0;
    int r = numsSize - 1;
    int mid = 0;
    while(l+1 < r){
        mid = l + (r-l)/2;
        if(nums[mid] == target)
            return mid;
        if(nums[mid] < nums[r]){
            //right is ordered
            //if target locates a right parits
            if(target <= nums[r] && target >= nums[mid])
                l = mid;
            else
                r = mid;
        }else{
            //left is ordered
            if(target<= nums[mid] && target >= nums[l])
                r = mid;
            else
                l = mid;
        }
    }
    
    if(nums[l] == target)
        return l;
    
    if(nums[r] == target)
        return r;
    
    return -1;
    
}