first_last_in_array

  • 2022-12-14
  • 浏览 (538)

first_last_in_array.cpp 源码

//  在排序数组中查找元素的第一个和最后一个位置

#include "iostream"
#include "vector"

using namespace std;

class Solution {
public:

    // 线性查找
    vector<int> searchRange1(vector<int>& nums, int target) {
        vector<int> res{-1, -1};
        for (int i = 0; i < nums.size(); i++) {
            if (nums[i] == target) {
                if (i == 0 || nums[i - 1] != target) {
                    res[0] = i;
                }
                if (i == nums.size() - 1 || nums[i + 1] != target) {
                    res[1] = i;
                }
            }
        }
        return res;
    }

    // 二分查找
    vector<int> searchRange2(vector<int>& nums, int target) {
        vector<int> res{-1, -1};
        int low = 0, high = nums.size() - 1;
        while(low <= high) {
            int mid = low + (high - low) / 2;
            if(nums[mid] < target) {
                low = mid + 1;
            } else if(nums[mid] > target) {
                high = mid - 1;
            } else {
                if(nums[low] == target && nums[high] == target) {
                    return {low, high};
                }
                if(nums[low] != target) {
                    low++;
                }
                if(nums[high] != target) {
                    high--;
                }
            }
        }
        return res;
    }
};

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