剑指 Offer 53 - I. 在排序数组中查找数字 I

题目来源：剑指 Offer 53 - I. 在排序数组中查找数字 I

统计一个数字在排序数组中出现的次数。

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var search = function(nums, target) {
    return nums.filter((val)=> val == target).length;
};

二分查找

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var search = function(nums, target) {
  let n = nums.length;
  let res = 0;
  var binarySearch = (nums, target) =>{
    let left = 0, right = n - 1;
    while(left <= right){
      let mid = Math.floor((left+right)/2);
      if(nums[mid] < target){
        left = mid + 1;
      }else if(nums[mid] > target){
        right = mid -1;
      }else{
        return mid;
      }
    }
    return -1;
  }
  let find = binarySearch(nums, target);
  if(find == -1)
  {
    return 0;
  }
  for(let i = find;i>=0;i--){
    if(nums[i] === target){
      res += 1;
    }else{
      break;
    }
  }
  
  for(let i = find+1;i<n;i++){
    if(nums[i] === target){
      res += 1;
    }else{
      break;
    }
  }
  return res;
};

示例 1:

输入: nums = [5,7,7,8,8,10], target = 8
输出: 2

示例 2:

输入: nums = [5,7,7,8,8,10], target = 6
输出: 0

 

限制：

0 <= 数组长度 <= 50000

 

注意：本题与主站 34 题相同（仅返回值不同）：https://leetcode-cn.com/problems/find-first-and-last-position-of-element-in-sorted-array/