3 sum answer

linfeng wu answered on October 15, 2024 Popularity 6/10 Helpfulness 1/10

answer 3 sum answer

related how to create a simple while loop in JavaScript

3 sum answer

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class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        Arrays.sort(nums);
        // n 为 3，从 nums[0] 开始计算和为 0 的三元组
        return nSumTarget(nums, 3, 0, 0);
    }

    // 注意：调用这个函数之前一定要先给 nums 排序
    // n 填写想求的是几数之和，start 从哪个索引开始计算（一般填 0），target 填想凑出的目标和
    private List<List<Integer>> nSumTarget(int[] nums, int n, int start, long target) {
        int sz = nums.length;
        List<List<Integer>> res = new ArrayList<>();
        // 至少是 2Sum，且数组大小不应该小于 n
        if (n < 2 || sz < n) return res;
        // 2Sum 是 base case
        if (n == 2) {
            // 双指针那一套操作
            int lo = start, hi = sz - 1;
            while (lo < hi) {
                int sum = nums[lo] + nums[hi];
                int left = nums[lo], right = nums[hi];
                if (sum < target) {
                    while (lo < hi && nums[lo] == left) lo++;
                } else if (sum > target) {
                    while (lo < hi && nums[hi] == right) hi--;
                } else {
                    res.add(new ArrayList<>(Arrays.asList(left, right)));
                    while (lo < hi && nums[lo] == left) lo++;
                    while (lo < hi && nums[hi] == right) hi--;
                }
            }
        } else {
            // n > 2 时，递归计算 (n-1)Sum 的结果
            for (int i = start; i < sz; i++) {
                List<List<Integer>> sub = nSumTarget(nums, n - 1, i + 1, target - nums[i]);
                for (List<Integer> arr : sub) {
                    // (n-1)Sum 加上 nums[i] 就是 nSum
                    arr.add(nums[i]);
                    res.add(arr);
                }
                while (i < sz - 1 && nums[i] == nums[i + 1]) i++;
            }
        }
        return res;
    }
}

Popularity 6/10 Helpfulness 1/10 Language whatever

Source: leetcode.com

Tags: sum whatever

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Contributed on Oct 16 2024

linfeng wu

0 Answers Avg Quality 2/10

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how to create a simple while loop in JavaScript

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let i = 0;
while(i<=10) {
  console.log(i);
  i++;
}

Popularity 2/10 Helpfulness 1/10 Language javascript

Source: Grepper

Tags: while-loop javascript

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Contributed on Oct 15 2024

Matthew “matwal” Walton

0 Answers Avg Quality 2/10

3 sum answer

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