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executable file
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/*
@filename 16.cpp
@author caonan
@date 2022-03-28 14:45:21
@reference 剑指offer专项
@url https://leetcode-cn.com/problems/wtcaE1/
@brief 给定一个字符串 s ，请你找出其中不含有重复字符的 最长连续子字符串的长度。
*/
#include <cassert>
#include <cstdio>
#include <algorithm>
#include <iostream>
#include <map>
#include <unordered_set>
#include <vector>
using namespace std;
class Solution {
public:
int lengthOfLongestSubstring(string s) {
int max_len = 0;
unordered_set<char> map_store;
int left = 0;
for (int right = 0; right < s.size();) {
if (map_store.find(s[right]) == map_store.end()) {
map_store.insert(s[right]);
max_len = std::max(max_len, right - left + 1);
++right;
} else {
map_store.erase(s[left++]);
}
}
return max_len;
}
// asii码有最多256个，可以用固定大小的的数组表示
int lengthOfLongestSubstring1(string s) {
vector<int> counts(256, 0);
// 每次都遍历了整个数组，效率不高
auto is_greater_than1 = [](const vector<int>& counts) -> bool {
for (const auto& v : counts) {
if (v > 1) {
return true;
}
}
return false;
};
int left = -1;
int max_len = 0;
for (int right = 0; right < s.size(); ++right) {
counts[s[right]]++;
while (is_greater_than1(counts)) {
++left;
counts[s[left]]--;
}
max_len = std::max(max_len, right - left);
}
return max_len;
}
// 在lengthOfLongestSubstring1的基础上优化掉遍历counts的开销
// 因为右边每次加入新元素，如果有重复，那必然大于1，于是left右移直到将counts[s[right]]减下去
int lengthOfLongestSubstring2(string s) {
vector<int> counts(256, 0);
int left = -1;
int max_len = 0;
for (int right = 0; right < s.size(); ++right) {
counts[s[right]]++;
while (counts[s[right]] > 1) {
++left;
counts[s[left]]--;
}
max_len = std::max(max_len, right - left);
}
return max_len;
}
};
int main() {
Solution s;
assert(s.lengthOfLongestSubstring("abcabcbb") == 3);
assert(s.lengthOfLongestSubstring("bbbbb") == 1);
assert(s.lengthOfLongestSubstring("pwwkew") == 3);
assert(s.lengthOfLongestSubstring("tmmzuxt") == 5);
assert(s.lengthOfLongestSubstring1("abcabcbb") == 3);
assert(s.lengthOfLongestSubstring1("bbbbb") == 1);
assert(s.lengthOfLongestSubstring1("pwwkew") == 3);
assert(s.lengthOfLongestSubstring1("tmmzuxt") == 5);
assert(s.lengthOfLongestSubstring2("abcabcbb") == 3);
assert(s.lengthOfLongestSubstring2("bbbbb") == 1);
assert(s.lengthOfLongestSubstring2("pwwkew") == 3);
assert(s.lengthOfLongestSubstring2("tmmzuxt") == 5);
return 0;
}