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| class Solution {
public String minWindow(String s, String t) {
Map<Character, Integer> need = new HashMap<>();
Map<Character, Integer> window = new HashMap<>();
for (int i = 0; i < t.length(); i++) {
need.merge(t.charAt(i), 1, (oldVal, newVal) -> ++oldVal);
}
int left = 0, right = 0, start = 0, valid = 0, len = s.length() + 1;
while (right < s.length()) {
char c = s.charAt(right);
right++;
if (need.containsKey(c)) {
window.merge(c, 1, (oldVal, newVal) -> ++oldVal);
if (need.get(c).equals(window.get(c))) {
valid++;
}
}
while (valid == need.size()) {
if (right - left < len) {
start = left;
len = right - left;
}
char l = s.charAt(left);
left++;
if (need.containsKey(l)) {
if (window.get(l).equals(need.get(l))) {
valid--;
}
window.compute(l, (k, v) -> --v);
}
}
}
return len == s.length() + 1 ? "" : s.substring(start, start + len);
}
}
|