滑动窗口法，0438，找到字符串中所有字母异位词

滑动窗口

Author: moralok

README.md

@@ -109,6 +109,7 @@
 |0415|字符串相加|简单||
 |[0425](https://leetcode-cn.com/tag/sliding-window/)|替换后的最长重复字符|中等|[sliding window](sliding_window)|
 |0437|路径总和 III|简单||
+|[0438](https://leetcode-cn.com/problems/find-all-anagrams-in-a-string/)|找到字符串中所有字母异位词|中等|[sliding window](sliding_window)|
 |0441|排列硬币|简单||
 |0447|回旋镖的数量|简单||
 |0448|找到所有数组中消失的数字|简单||

sliding_window/Lc0438Solution.java

@@ -0,0 +1,58 @@
+package sliding_window;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+public class Lc0438Solution {
+    public List<Integer> findAnagrams(String s, String p) {
+        if (s == null || s.length() < p.length()) {
+            return Collections.emptyList();
+        }
+        int[] windows = new int[26];
+        int[] need = new int[26];
+        for (int i = 0; i < p.length(); i++) {
+            need[p.charAt(i)-'a']++;
+            windows[s.charAt(i)-'a']++;
+        }
+        int count = 0;
+        for (int i = 0; i < 26; i++) {
+            if (windows[i] == need[i]) {
+                count++;
+            }
+        }
+        List<Integer> ret = new ArrayList<>();
+        if (count == 26) {
+            ret.add(0);
+        }
+        int pLen = p.length();
+        for (int i = 0; i < s.length() - pLen; i++) {
+            int l = s.charAt(i) - 'a', r = s.charAt(i + pLen) - 'a';
+            windows[r]++;
+            if (windows[r] == need[r]) {
+                count++;
+            } else if (windows[r] == need[r] + 1) {
+                count--;
+            }
+            // 顺序很重要
+            windows[l]--;
+            if (windows[l] == need[l]) {
+                count++;
+            } else if (windows[l] == need[l] - 1) {
+                count--;
+            }
+            if (count == 26) {
+                // emmm
+                ret.add(i+1);
+            }
+        }
+        return ret;
+    }
+
+    public static void main(String[] args) {
+        Lc0438Solution solution = new Lc0438Solution();
+        String s = "cbaebabacd";
+        String p = "abc";
+        System.out.println(solution.findAnagrams(s, p));
+    }
+}

sliding_window/README.md

@@ -6,4 +6,5 @@
 |[0395](https://leetcode-cn.com/problems/longest-substring-with-at-least-k-repeating-characters/)|至少有K个重复字符的最长子串|中等|是|
 |[0425](https://leetcode-cn.com/tag/sliding-window/)|替换后的最长重复字符|中等|是|
 |[0159](https://leetcode-cn.com/problems/longest-substring-with-at-most-two-distinct-characters/)|至多包含两个不同字符的最长子串|中等|是|
-|[0340](https://leetcode-cn.com/problems/longest-substring-with-at-most-k-distinct-characters/)|至多包含 K 个不同字符的最长子串|中等|是|
+|[0340](https://leetcode-cn.com/problems/longest-substring-with-at-most-k-distinct-characters/)|至多包含 K 个不同字符的最长子串|中等|是|
+|[0438](https://leetcode-cn.com/problems/find-all-anagrams-in-a-string/)|找到字符串中所有字母异位词|中等|是|