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public class MinimumWindowSubstring {
public String minWindow(String s, String t) {
if (t == null || t.isEmpty()) {
return "";
}
if (s == null || s.isEmpty()) {
return null;
}
Map<Character, Integer> tMap = new HashMap<Character, Integer>();
for (int i = 0; i < t.length(); i++) {
char c = t.charAt(i);
if (tMap.containsKey(c)) {
tMap.put(c, tMap.get(c) + 1);
} else {
tMap.put(c, 1);
}
}
Map<Character, Integer> countMap = new HashMap<Character, Integer>();
int matchCount = 0;
int start = 0;
String min = "";
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if (tMap.containsKey(c)) {
if (countMap.containsKey(c)) {
if (countMap.get(c) < tMap.get(c)) {
matchCount++;
}
countMap.put(c, countMap.get(c) + 1);
} else {
countMap.put(c, 1);
matchCount++;
}
}
if (matchCount == t.length()) {
char tmp = s.charAt(start);
while (start < s.length() && (!countMap.containsKey(tmp) || countMap.get(tmp) > tMap.get(tmp))) {
if (countMap.containsKey(tmp)) {
countMap.put(tmp, countMap.get(tmp) - 1);
}
start++;
tmp = s.charAt(start);
}
if (min.isEmpty() || i + 1 - start < min.length()) {
min = s.substring(start, i + 1);
}
}
}
return min;
}
@Test
public void test() {
String s = "a";
String t = "aa";
String result = minWindow(s, t);
}
}
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