本文共 768 字，大约阅读时间需要 2 分钟。

function missingNumber(nums){  let len = nums.length;  let arr = [];  for(let i = 0; i <= len; i++){    arr[i] = i;  }  arr = arr.filter(el => !nums.includes(el));  return arr[0];}let arr1 = [1,2,3,4,5,6,7,9];let arr2 = [0,1,3];

function missingNumber(nums){  let len = nums.length;  for(let i = 0; i < len; i++){    if(nums[i] != i){      return i;    }  }}let arr1 = [0,1,2,3,4,5,6,7,9];let arr2 = [0,1,3];

这种情况不适用于length == 1 

var missingNumber = function(nums) {    //二项查找    if(nums.length - 1 === nums[nums.length - 1]) return nums.length;//如果就是有序，直接返回最后一个数    let left = 0, right = nums.length - 1;    while(left <= right) {        let mid = left + parseInt((right - left) / 2);        mid === nums[mid] ? left = mid + 1 : right = mid - 1;    }    return left;};

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