每天一点LeetCode

//题解里luobo大佬提供的思路 ：https://leetcode-cn.com/problems/add-two-numbers/solution/liang-shu-xiang-jia-jian-dan-yi-dong-by-luobo-3/
var addTwoNumbers = function(l1, l2) {
    let node = new ListNode('head')
    let temp = node , sum , n = 0
    while( l1 || l2 ){
        const n1 = l1 ? l1.val : 0
        const n2 = l2 ? l2.val : 0
        sum = n1 + n2 + n
        temp.next = new ListNode( sum % 10 )
        temp = temp.next
        n = parseInt( sum / 10 )
        if(l1) l1 = l1.next
        if(l2) l2 = l2.next
    }
    if( n > 0 ) temp.next = new ListNode(n)
    return node.next
};

    // 作者：LeetCode-Solution
    // 链接：https://leetcode-cn.com/problems/longest-substring-without-repeating-characters/solution/wu-zhong-fu-zi-fu-de-zui-chang-zi-chuan-by-leetc-2/
var lengthOfLongestSubstring = function(s) {
    // 哈希集合，记录每个字符是否出现过
    const occ = new Set();
    const n = s.length;
    // 右指针，初始值为 -1，相当于我们在字符串的左边界的左侧，还没有开始移动
    let rk = -1, ans = 0;
    for (let i = 0; i < n; ++i) {
        if (i != 0) {
            // 左指针向右移动一格，移除一个字符
            occ.delete(s.charAt(i - 1));
        }
        while (rk + 1 < n && !occ.has(s.charAt(rk + 1))) {
            // 不断地移动右指针
            occ.add(s.charAt(rk + 1));
            ++rk;
        }
        // 第 i 到 rk 个字符是一个极长的无重复字符子串
        ans = Math.max(ans, rk - i + 1);
    }
    return ans;
};

var lengthOfLongestSubstring = function(s) {
    let arr = [], max = 0
    for(let i = 0; i < s.length; i++) {
        let index = arr.indexOf(s[i])
        if(index !== -1) {
            arr.splice(0, index+1);
        }
        arr.push(s.charAt(i))
        max = Math.max(arr.length, max) 
    }
    return max
};

// 作者：user7746o
// 链接：https://leetcode-cn.com/problems/longest-substring-without-repeating-characters/solution/zi-jie-leetcode3wu-zhong-fu-zi-fu-de-zui-chang-zi-/
// 来源：力扣（LeetCode）
// 著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

var findMedianSortedArrays = (nums1, nums2) => {
  let len1 = nums1.length, len2 = nums2.length
  if (len1 > len2) return findMedianSortedArrays(nums2, nums1)
  let len = len1 + len2
  let start = 0, end = len1 
  let partLen1, partLen2 

  while (start <= end) {
    partLen1 = (start + end) >> 1
    partLen2 = ((len + 1) >> 1) - partLen1

    let L1 = partLen1 === 0 ? -Infinity : nums1[partLen1 - 1]
    let L2 = partLen2 === 0 ? -Infinity : nums2[partLen2 - 1]
    let R1 = partLen1 === len1 ? Infinity : nums1[partLen1]
    let R2 = partLen2 === len2 ? Infinity : nums2[partLen2]

    if (L1 > R2) {
      end = partLen1 - 1
    } else if (L2 > R1) {
      start = partLen1 + 1
    } else { // L1 <= R2 && L2 <= R1
      return len % 2 === 0 ?
        (Math.max(L1, L2) + Math.min(R1, R2)) / 2 :
        Math.max(L1, L2)
    }
  }
}

//作者：hyj8
//链接：https://leetcode-cn.com/problems/median-of-two-sorted-arrays/solution/fen-duan-jie-fa-zhen-shi-miao-a-by-hyj8/
// 来源：力扣（LeetCode）
//著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

var longestPalindrome = function (s) {
    if (!s || !s.trim()) return '';
    if (s.length === 1) return s;
    if (s.length === 2) return s[0] === s[1] ? s[0] + s[1] : s[0];
    
    var sArray = s.split('');
    var x = [...new Set(sArray)];
    var result;
    var result1;
    var result2;
    
    if (x.length === 1) return s;

    // 以item为对称点 找到回文串
    result1 = sArray.reduce(function(memo, item, idx, self) {
        var ret;

        if (idx === 0 ) return memo;
        if (typeof self[idx - 1] !== 'string' || self[idx - 1] !== self[idx + 1]) return memo;
        
        memo = (function () {
            var middle = idx;
            var i = 1;
            var result = item;
            
            while (typeof self[middle + i] === 'string' && typeof self[middle - i] === 'string' && self[middle + i] === self[middle - i]) {
                ++i;
            }
            
            if (i === 1) {                
                return memo;
            }
            
            i = i -1;
            result = self.slice(middle - i, middle + i+1).join('');

            return result.length > (memo && memo.length || 1) ? result : memo; 
        })();    
        
        return memo;
    }, sArray[0]);
    
    // 以item 和 next 两个一起为对称点 找到回文串
    result2 = sArray.reduce(function(memo, item, idx, self) {
         // axxa 中心轴是两个字母
        if (item !== self[idx + 1]) return memo;
        memo = (function () {
            var left = idx;
            var right = idx + 1;
            var i = 1;
            var result = item + item;
            
            while (typeof self[right + i] === 'string' &&typeof self[left - i] === 'string' && self[left - i] === self[right + i]) {
                ++i;
            }

            if (i === 1) return result.length > (memo && memo.length || 1) ? result : memo;
            
            i = i - 1;
            result = self.slice(left - i, right + i + 1).join('');

            return result.length > (memo && memo.length || 1)? result : memo;   
        })();

        return memo;
        
    }, sArray[0]);

    return result1.length > result2.length ? result1 : result2;   
}

//作者：chubby-2
//链接：https://leetcode-cn.com/problems/longest-palindromic-substring/solution/zui-chang-hui-wen-zi-chuan-by-chubby-2/
//来源：力扣（LeetCode）
//著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。