目录
[2. 字母异位词分组](#2. 字母异位词分组)
[3. 最长连续序列](#3. 最长连续序列)
[1. 移动零](#1. 移动零)
[2. 盛最多水的容器](#2. 盛最多水的容器)
[3. 三数之和](#3. 三数之和)
[4. 接雨水](#4. 接雨水)
[1. 无重复字符的最长子串](#1. 无重复字符的最长子串)
[2. 找到字符串中所有字母异位词](#2. 找到字符串中所有字母异位词)
前言
一、哈希：两数之和，字母异位词分组，最长连续序列。
二、双指针：移动零，盛最多水的容器，三数之和，接雨水。
三、滑动窗口：无重复字符的最长子串，找到字符串中所有字母异位词。
一、哈希
1.两数之和
python
class Solution(object):
def twoSum(self, nums, target):
n = len(nums)
for i in range(n):
for j in range(i+1, n):
if nums[i] + nums[j] == target:
return [i, j]2. 字母异位词分组
原题链接：49. 字母异位词分组 - 力扣（LeetCode）
python
class Solution(object):
def groupAnagrams(self, strs):
res = []
dicts = {}
for s in strs:
s_ = ''.join(sorted(s))
if s_ in dicts:
dicts[s_].append(s)
else:
dicts[s_] = [s]
return list(dicts.values())3. 最长连续序列
原题链接：128. 最长连续序列 - 力扣（LeetCode）
python
class Solution(object):
def longestConsecutive(self, nums):
# left, right双指针
res = 0
nums = set(nums)
for left in nums:
if left-1 not in nums: # 找片段左端点left
right = left + 1
while right in nums: # 找片段右端点right
right += 1
res = max(res, right-left)
return res二、双指针
1. 移动零
python
class Solution(object):
def moveZeroes(self, nums):
for i, n in enumerate(nums):
if n == 0:
nums.remove(n)
nums.append(n)
return nums2. 盛最多水的容器
原题链接：11. 盛最多水的容器 - 力扣（LeetCode）
python
# 考点：左右指针（left & right）
class Solution(object):
def maxArea(self, height):
n = len(height)
left, right = 0, n-1
res = 0
while left < right:
area = min(height[left], height[right]) * (right - left)
res = max(res, area)
if height[left] <= height[right]:
left +=1
else:
right -=1
return res3. 三数之和
python
# 考点：左右指针（left & right）
class Solution(object):
def threeSum(self, nums):
nums.sort()
if min(nums) > 0:
return []
n = len(nums)
res = []
for i in range(n):
if i>0 and nums[i] == nums[i-1]:
continue
left, right = i+1, n-1
while left < right:
if nums[i]+nums[left]+nums[right] == 0:
while left < right and nums[left] == nums[left+1]:
left += 1
while left < right and nums[right] == nums[right-1]:
right -= 1
res.append([nums[i], nums[left], nums[right]])
left += 1
right -= 1
elif nums[i]+nums[left]+nums[right] < 0:
left += 1
else:
right -= 1
return res4. 接雨水
python
class Solution(object):
def trap(self, height):
# prefix_max最大前缀, suffix_max最大后缀, min(prefix_max, suffix_max) - h
res = 0
n = len(height)
prefix_max = [0] * n
prefix_max[0] = height[0]
for i in range(1, n):
prefix_max[i] = max(prefix_max[i-1], height[i])
suffix_max = [0] * n
suffix_max[-1] = height[-1]
for i in range(n-2, -1, -1):
suffix_max[i] = max(height[i], suffix_max[i+1])
for h, prefix, suffix in zip(height, prefix_max, suffix_max):
res = res + min(prefix, suffix) - h
return res三、滑动窗口
1. 无重复字符的最长子串
原题链接：3. 无重复字符的最长子串 - 力扣（LeetCode）
python
# 考点：滑窗（不定窗口），快慢指针
class Solution(object):
def lengthOfLongestSubstring(self, s):
from collections import Counter
cnt = Counter()
left = 0
res = 0
for right, c in enumerate(s):
cnt[c] += 1
while cnt[c] > 1:
cnt[s[left]] -= 1
left += 1
res = max(res, right-left+1)
return res2. 找到字符串中所有字母异位词
原题链接：438. 找到字符串中所有字母异位词 - 力扣（LeetCode）
python
class Solution(object):
def findAnagrams(self, s, p):
# 考点：滑窗（固定窗口），快慢指针
from collections import Counter
left = 0
res = []
cnt_p = Counter(p)
cnt_s = Counter()
for right, c in enumerate(s):
cnt_s[c] += 1
while right - left + 1 == len(p):
if cnt_s == cnt_p:
res.append(left)
if s[left] in cnt_s:
cnt_s[s[left]] -= 1
if cnt_s[s[left]] == 0:
del cnt_s[s[left]]
left += 1
return res