33. Search in Rotated Sorted Array

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二分查找的扩展

class Solution {
public:
    int search(vector& nums, int target) {
        if(nums.empty()) return -1;
        int start = 0;
        int end = nums.size() - 1;
        while(start + 1 < end){
            int mid = start + (end - start) / 2;
            if(target == nums[mid]) return mid;
            if(nums[start] < nums[mid]){//可判断start 到 mid 是有序的。
                if(target >= nums[start] && target <= nums[mid]){
                    end = mid;
                }
                else{
                    start = mid;
                }
            }
            else{ // 可判断mid 到 end 是有序的
                if(target >= nums[mid] && target <= nums[end]){
                    start = mid;
                }
                else{
                    end = mid;
                }
            }
        }
        if(nums[start] == target) return start;
        if(nums[end] == target ) return end;
        return -1;
        
    }
};