第一种是无重复的，也就是说左边和右边不会相等
33.Search in Rotated Sorted Array
class Solution {
public:
int search(vector<int>& nums, int target) {
int l = 0, r = nums.size() - 1;
while (l <= r) {
int mid = (l + r) / 2;
if (nums[mid] == target) {
return mid;
}
else if (nums[l] <= nums[mid]) {
if (nums[l] <= target && target <= nums[mid]) {
r = mid - 1;
}
else {
l = mid + 1;
}
}
else {
if (nums[mid] < target && target <= nums[r]) {
l = mid + 1;
}
else {
r = mid - 1;
}
}
}
return -1;
}
};
第二种是有重复的，可能nums[l]==nums[r]，这个要注意。
如81.Search in Rotated Sorted Array II
class Solution {
public:
bool search(vector<int>& nums, int target) {
int l = 0, r = nums.size() - 1;
while (l <= r) {
int mid = (l + r) / 2;
if (nums[mid] == target) {
return true;
}
if (nums[l] == nums[mid] && nums[mid] == nums[r]) {
l++;
r--;
}
else if (nums[l] <= nums[mid]) {
if (nums[l] <= target && target <= nums[mid]) {
r = mid - 1;
}
else {
l = mid + 1;
}
}
else {
if (nums[mid] <= target && target <= nums[r]) {
l = mid + 1;
}
else {
r = mid - 1;
}
}
}
return false;
}
};