LeetCode 76. Minimum Window Substring

#include <string>#include <unordered_map>#include <vector>#include <iostream>using namespace std;/*  Given a string S and a string T, find the minimum window in S which will contain all the  characters in T in complexity O(n).   For example:  S = "ADOBECODEBANC"  T = "ABC"  minumum window is "BANC".  If there is no such window in S that convers all characters in T, return the empty string "".*/string minWindow(string s, string t) {  int minLen = s.size()+1;  int minBegin = 0;  int tSize = t.size();  vector<int> count(256, 0);  vector<int> needed(256, 0);  for(int i = 0; i < tSize; ++i) {      needed[t[i]]++;  }  int tCount = 0;  for(int begin = 0, end = 0; end < s.size(); ++end) {    char tmp = s[end];    if(!needed[tmp]) continue;    /* find the longest length that contains all the t chars.*/    if(++count[tmp] <= needed[tmp]) {        tCount++;    }    /* shrink the range to find the shortest one.*/    if(tCount == tSize) {      /* think about this case "AAAABC"*/      while(needed[s[begin]] == 0 || count[s[begin]] > needed[s[begin]]) {        if(count[s[begin]] > needed[s[begin]]) {count[s[begin]]--;};        begin++;      }      int length = end - begin + 1;      if(length < minLen) {        minLen = length;        minBegin = begin;      }    }  }  return minLen > s.size() ? "" : s.substr(minBegin, minLen);}int main(void) {  cout << minWindow("ADOBECODEBANC", "ABC") << endl;} 

Facebook asked a simplified version.

#include "header.h"using namespace std;string minWindowSubstring(string str, unordered_set<char> chars) {  unordered_map<char, int> charToCount;  int windowSize = str.size() + 1, minStart = 0;  int count = 0;  for(int start = 0, end = 0; end < str.size(); ++end) {    char ch = str[end];    if(chars.find(ch) == chars.end()) continue;    if(charToCount[ch] == 0) {count++; charToCount[ch] = 1;}    else charToCount[ch]++;    if(count == chars.size()) {    cout << "count size : " << count << " "<< "charToCount.size() : " << charToCount.size() << endl; // it is very weird here.      while((chars.find(str[start]) == chars.end()) || (charToCount[str[start]] > 1)) {        if(charToCount[str[start]] > 1) charToCount[str[start]]--;        start++;      }      int size = end - start + 1;      if(windowSize > size) {        windowSize = size;        minStart = start;      }    }  }  return windowSize > str.size() ? "" : str.substr(minStart, windowSize);}int main(void) {  unordered_set<char> inputs{'a', 'b', 'c'};  cout << minWindowSubstring("adabbcbbabc", inputs) << endl;}