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前言
一、力扣76. 最小覆盖子串
class Solution {
public String minWindow(String s, String t) {
Map<Character,Integer> need = new HashMap<>();
Map<Character,Integer> window = new HashMap<>();
for(char c : t.toCharArray()){
need.put(c,need.getOrDefault(c,0)+1);
}
int left = 0, right = 0, indexLeft = 0, len = Integer.MAX_VALUE, vaild = 0;
while(right < s.length()){
char c = s.charAt(right);
right ++;
//扩大窗口
if(need.containsKey(c)){
window.put(c,window.getOrDefault(c,0)+1);
if(window.get(c).equals(need.get(c))){
vaild ++;
}
}
//缩小窗口
while(vaild == need.size()){
//更新收集结果
if(right - left < len){
len = right - left;
indexLeft = left;
}
char cur = s.charAt(left);
left ++;
//缩小窗口
if(need.containsKey(cur)){
if(need.get(cur).equals(window.get(cur))){
vaild --;
}
window.put(cur,window.get(cur)-1);
}
}
}
return len == Integer.MAX_VALUE ? "" : s.substring(indexLeft,indexLeft+len);
}
}
二、力扣567. 字符串的排列
class Solution {
public boolean checkInclusion(String s1, String s2) {
Map<Character,Integer> need = new HashMap<>();
Map<Character,Integer> window = new HashMap<>();
for(char c : s1.toCharArray()){
need.put(c,need.getOrDefault(c,0)+1);
}
int left = 0, right = 0, vaild = 0; boolean flag = false;
while(right < s2.length()){
char c = s2.charAt(right);
right ++;
if(need.containsKey(c)){
window.put(c,window.getOrDefault(c,0)+1);
if(need.get(c).equals(window.get(c))){
vaild ++;
}
}
while(right - left >= s1.length()){
if(vaild == need.size()){
return true;
}
char cur = s2.charAt(left);
left ++;
if(need.containsKey(cur)){
if(need.get(cur).equals(window.get(cur))){
vaild --;
}
window.put(cur,window.get(cur)-1);
}
}
}
return false;
}
}
三、力扣438. 找到字符串中所有字母异位词
class Solution {
public List<Integer> findAnagrams(String s, String p) {
List<Integer> res = new ArrayList<>();
Map<Character, Integer> need = new HashMap<>();
Map<Character, Integer> window = new HashMap<>();
for(char c : p.toCharArray()){
need.put(c,need.getOrDefault(c,0)+1);
}
int left = 0, right = 0, vaild = 0;
while(right < s.length()){
//窗口扩大
char c = s.charAt(right);
right ++;
//调整窗口
if(need.containsKey(c)){
window.put(c,window.getOrDefault(c,0)+1);
if(window.get(c).equals(need.get(c))){
vaild ++;
}
}
while(right - left >= p.length()){
//收集
if(vaild == need.size()){
res.add(left);
}
//缩小窗口
char cur = s.charAt(left);
left ++;
//调整窗口
if(need.containsKey(cur)){
if(window.get(cur).equals(need.get(cur))){
vaild --;
}
window.put(cur,window.get(cur)-1);
}
}
}
return res;
}
}
四、力扣3. 无重复字符的最长子串
class Solution {
public int lengthOfLongestSubstring(String s) {
int res = 0;
Map<Character, Integer> window = new HashMap<>();
int left = 0, right = 0;
while(right < s.length()){
char c = s.charAt(right);
right ++;
window.put(c,window.getOrDefault(c,0)+1);
while(window.get(c) > 1){
char cur = s.charAt(left);
left ++;
window.put(cur,window.get(cur)-1);
}
res = Math.max(res,right-left);
}
return res;
}
}
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