Leetcode 33. 搜索旋转排序数组

class Solution {
public:
int search(vector<int>& nums, int target) {
int beg = 0;
int end = nums.size()-1;
while(beg <= end)
{
int mid = beg + (end-beg)/2;
//找到就直接返回
if(target == nums[mid])
return mid;

else if( target < nums[mid])
{
if(nums[beg] < nums[mid])//[beg, mid]是递增区间 [mid+1, end]包含了旋转区间
{
if(target >= nums[beg])  // 递增区间 直接用二分就可以了
{
end = mid -1;
}// 表明可能在后面的旋转区间里面
else
{
beg = mid +1;
}
}
else if(nums[beg] > nums[mid]) //[beg, mid]是旋转区间 [mid+1, end]包含了递增区间
{
end = mid -1;
}//前提是 target < nums[mid]  仅当还剩下两个数的时候，就相当于是target < nums[beg] 因此应该
else if(nums[beg] == nums[mid])
{
beg = mid+1;
}
}//
else if(target > nums[mid])
{
if(nums[beg] < nums[mid])//[beg,mid]是递增区间，[mid+1, end]包含了旋转区间
{
beg  = mid+1;
}
else if(nums[beg] > nums[mid])//前面是旋转区间，后面是递增区间，
{
if(target >= nums[beg])//nums[beg] > nums[end]
{
end = mid -1;
}
else
{
beg = mid +1;
}
}// 如果仅仅剩下两个元素了，target > nums[mid]
else if(nums[beg] == nums[mid])
{
beg = mid +1;
}
}
}
return -1;
}
};