【重点!】【二分查找】33.搜索旋转排序数组

题目

法1：二分查找

Python

class Solution:
    def search(self, nums: List[int], target: int) -> int:
        l = 0
        r = len(nums)-1
        while l <= r:
            mid = (l + r) // 2
            if nums[mid] == target:
                return mid
            elif nums[mid] < nums[r]:  # 跟右端索引数值对比！！！
                if nums[mid] < target <= nums[r]: 
                    l = mid + 1
                else:
                    r = mid - 1
            else:
                if nums[l] <= target < nums[mid]: 
                    r = mid - 1
                else:
                    l = mid + 1

        return -1

Java

根据mid来分段，此思路需要牢记！！！

class Solution {
    public int search(int[] nums, int target) {
        int n = nums.length;
        int l = 0, r = n - 1;
        while (l <= r) {
            int mid = l + (r - l) / 2;
            if (nums[mid] == target) {
                return mid;
            }
            if (nums[mid] > nums[r]) { // 左段
                if (target < nums[mid] && target >= nums[l]) {
                    r = mid - 1;
                } else {
                    l = mid + 1;
                }
            } else {                   // 右段
                if (target > nums[mid] && target <= nums[r]) {
                    l = mid + 1;
                } else {
                    r = mid - 1;
                }
            }
        }

        return -1; 
    }
}