65 lines
1.4 KiB
C++
65 lines
1.4 KiB
C++
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// Source : https://oj.leetcode.com/problems/longest-substring-with-at-most-two-distinct-characters/
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// Author : Hao Chen
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// Date : 2014-12-01
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/*
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* Given a string, find the length of the longest substring T that contains at most 2 distinct characters.
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*
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* For example, Given s = “eceba”,
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*
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* T is "ece" which its length is 3.
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*/
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#include <iostream>
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#include <string>
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using namespace std;
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/*
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* Idea:
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*
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* 1) Using a map to count every chars.
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* 2) Using a 'cnt' to count the current distinct chars.
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* 3) if `cnt > 2`, then go through the previous substring to remove one char
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*
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* The following algorithm run-time complexity is O(n^2)
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*
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* This solution can be easy to extend to "find the length of longest substring with at most K distinct char(s)"
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*/
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int lengthOfLongestSubstringTwoDistinct(string s) {
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int maxLen = 0;
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char charMap[256] = {0};
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int wordCnt = 0;
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int start = 0;
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for(int i=0; i<s.size(); i++){
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if ( charMap[s[i]]++ == 0 ){
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wordCnt++;
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}
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while (wordCnt>2){
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charMap[s[start]]--;
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if (charMap[s[start]]==0){
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wordCnt--;
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}
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start++;
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}
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maxLen = max(maxLen, i - start + 1);
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}
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return maxLen;
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}
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int main(int argc, char** argv)
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{
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string s = "eceba";
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if (argc>1){
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s = argv[1];
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}
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cout << s << " : " << lengthOfLongestSubstringTwoDistinct(s) << endl;
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return 0;
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}
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