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# Javascript in Leetcode 01–03 | 面試問題

Pheezx Coding

### 01. Two sum

```Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Explanation: Because nums + nums == 9, we return [0, 1].
```

solution

```function twoSum(nums, target) {
const comp = new Map();
const len = nums.length;

for(let i=0; i < len; i++){
if(comp[nums[i]] >= 0){
return [comp[nums[i]], i];
}
comp[target- nums[i]] = i;
}
return [];
}
const nums = [2,7,11,15];
console.log(twoSum(nums,9));
```

leetcode problems | here

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
```Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [7,0,8]
Explanation: 342 + 465 = 807.
```

Solution

```var addTwoNumbers = function(l1, l2) {
let carry = 0;
let previousNode = new ListNode();
while(l1 || l2 || carry) {
let val1 = 0;
let val2=0;
if(l1) {
val1=l1.val;
l1=l1.next;
}
if(l2) {
val2=l2.val;
l2=l2.next;
}
const sum = val1 + val2 + carry;
carry = Math.floor(sum / 10);
const digit = sum % 10;
const currentNode =  new ListNode(digit);
previousNode.next = currentNode;
previousNode = currentNode;
}
};
```

### 03. Longest Substring Without Repeating Characters

```Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.
```

Constraints:

• `0 <= s.length <= 5 * 104`
• `s` consists of English letters, digits, symbols and spaces.

Solution

```var lengthOfLongestSubstring = function(s) {
let max = 0
let begin = 0
let set = new Set()

for(let end = 0; end < s.length; end++){
while(set.has(s[end])){
set.delete(s[begin])
begin = begin + 1
}
max = Math.max(max, end - begin + 1)
}
return max

};
```

leetcode problems | here

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