leetcode/cpp/0033.cpp at master · xfmeng17/leetcode · GitHub

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class Solution {
public:
  int search(vector<int> &nums, int target) {
    // return func1(nums, target);
    return func2(nums, target);
  }

  // ** my straight forward solution
  // ** use binary search find min index
  int func1(vector<int> &nums, int target) {
    int lo = 0, hi = nums.size() - 1;
    while (lo < hi) {
      int mid = (hi + lo) / 2;
      if (nums[mid] > nums[hi]) {
        lo = mid + 1;
      } else {
        hi = mid;
      }
    }
    int rotate = lo;

    lo = 0, hi = nums.size() - 1;
    while (lo <= hi) {
      int mid = (lo + hi) / 2;
      int realmid = (mid + rotate) % nums.size();
      if (nums[realmid] == target) {
        return realmid;
      } else if (nums[realmid] > target) {
        hi = mid - 1;
      } else {
        lo = mid + 1;
      }
    }

    return -1;
  }

  // 2019-10-07
  // 1. find rotate point
  // 2. find target in two segments divide by rotate point
  int func2(vector<int> &nums, int target) {
    int rotate = findRotate(nums);
    int index1 = binarySearch(nums, 0, rotate - 1, target);
    int index2 = binarySearch(nums, rotate, nums.size() - 1, target);

    if (index1 == -1 && index2 == -1) {
      return -1;
    }

    return index1 != -1 ? index1 : index2;
  }

  int findRotate(vector<int> &nums) {
    int lo = 0, hi = nums.size() - 1;

    while (lo < hi) {
      int mid = (lo + hi) / 2;
      if (nums[mid] > nums[hi]) {
        lo = mid + 1;
      } else {
        hi = mid;
      }
    }

    return lo;
  }

  int binarySearch(vector<int> &nums, int lo, int hi, int target) {
    if (hi >= nums.size()) {
      return -1;
    }

    while (lo <= hi) {
      int mid = (lo + hi) / 2;
      if (nums[mid] == target) {
        return mid;
      } else if (nums[mid] < target) {
        lo = mid + 1;
      } else {
        hi = mid - 1;
      }
    }

    return -1;
  }
};