leetcode 缺失数字

Posted 2022-05-23 lj96

给定一个包含 0, 1, 2, ..., n 中 n 个数的序列，找出 0 .. n 中没有出现在序列中的那个数。

示例 1:

输入: [3,0,1]
输出: 2

示例 2:

输入: [9,6,4,2,3,5,7,0,1]
输出: 8

方法1：排序去重查找

var missingNumber = function (nums) 
            var naturalNum = 0;
            var newArr = [];
            function sortNumber(a,b) 
                return a - b;
            
            nums.sort(sortNumber);
            for (let i = 0; i < nums.length; i++) 
                if (newArr.indexOf(nums[i]) === -1) 
                    newArr.push(nums[i]);
                
            
            for (let i = 0; i < newArr.length; i++)        
                if (newArr[i] === naturalNum) 
                    naturalNum++;
                    if (naturalNum === newArr.length) 
                        return naturalNum;
                    
                    continue;
                 else 
                    return naturalNum;
                
            
        ;

 

方法2：下标查找

var missingNumber = function (nums) 
    var len = nums.length;
    for(let i = 0;i < len;i++) 
        if(nums.indexOf(i) === -1) 
            return i;
        
    
    return len;
;

 

方法3：求差

var missingNumber = function (nums) 
    var sum1 = 0;
    var sum2 = (1 + nums.length) * nums.length / 2;
    nums.map(item => sum1 += item);
    return sum2 - sum1;
;