leetcode之两、三、四、最近接之和题目

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原创最新推荐文章于 2026-03-13 00:27:39 发布 362 阅读 AI 写同款· GEO 优化 ›

class Solution(object):
    def twoSum(self, nums, target):
        d = {}
        for i in range(len(nums)):
            diff = target - nums[i]
            if diff in d:
                return [i, d[diff]]
            d[nums[i]] = i
        
        return [-1, -1]

15. 三数之和

class Solution(object):
    def threeSum(self, nums):

        nums.sort()
        res = []
        for i in range(len(nums)):
            if i >0 and nums[i] == nums[i-1]: continue
            m, n = i+1, len(nums)-1
            while m <n:
                cur_sum = nums[i] + nums[m] + nums[n]
                if cur_sum > 0: 
                    n -= 1
                elif cur_sum<0:
                    m += 1
                else:
                    res.append([nums[i], nums[m], nums[n]])
                    m += 1
                    n -= 1
                    while m<n and nums[n] == nums[n+1]:
                        n -= 1
                    while m<n and nums[m-1] == nums[m]:
                        m += 1
        
        return res

16. 最接近的三数之和

class Solution(object):
    def threeSumClosest(self, nums, target):
        nums.sort()
        res = -1000000

        res = nums[0] + nums[1] + nums[2]
    
        for i in range(len(nums)):
            j, k = i+1, len(nums)-1
            while j<k:
                cur_sum = nums[i] + nums[j] + nums[k]
                if abs(cur_sum-target) < abs(res - target):
                    res = cur_sum
                if cur_sum == target:
                    return target
                if cur_sum> target:
                   k = k-1
                else:
                    j = j+1
        return res

454. 四数相加 II

from collections import Counter
class Solution(object):
    def fourSumCount(self, nums1, nums2, nums3, nums4):
        res = 0
        addCount = Counter(u+v for u in nums3 for v in nums4)
        for a in nums1:
            for b in nums2:
                res += addCount[-a-b]
        return res

18. 四数之和

class Solution(object):
    def fourSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[List[int]]
        """
        nums.sort()
        res = []
        for i in range(len(nums)):
            if i>0 and  nums[i-1] == nums[i]: continue
            for j in range(i+1, len(nums)):
                if j>i+1 and  nums[j-1] == nums[j]: continue
                m, n = j+1, len(nums)-1
                while m < n:
                    cur_sum = nums[i] + nums[j] + nums[m] + nums[n]
                    if cur_sum > target:
                        n -= 1
                    elif cur_sum < target:
                        m += 1
                    else:
                        res.append([nums[i],nums[j],nums[m],nums[n]])
                        m += 1
                        n -= 1
                        while m<n and nums[n] == nums[n+1]:
                            n -= 1
                        while m<n and nums[m] == nums[m-1]:
                            m += 1
        return res