add

Author: momo1314

magical&Double pointer/find-all-anagrams-in-a-string-438.java

@@ -0,0 +1,41 @@
+/**
+ * 滑动窗口解法，双指针
+ */
+class Solution {
+    public List<Integer> findAnagrams(String s, String p) {
+        if(s == null || s.length() == 0) return new ArrayList<>();
+        List<Integer> res = new ArrayList<>();
+        int[] needs = new int[26];
+        int[] windows = new int[26];
+        int left = 0 , right = 0 , total = p.length();
+
+        for(char a : p.toCharArray()) {
+            needs[a - 'a']++;
+        }
+
+        while(right < s.length()) {
+            char now = s.charAt(right);
+            if(needs[now - 'a'] > 0) {
+                windows[now - 'a']++;
+                if(windows[now - 'a'] <= needs[now - 'a']) {
+                    total -= 1;
+                }
+            }
+            while(total == 0) {
+                if(right-left+1 == p.length()){
+                    res.add(left);
+                }
+                char c = s.charAt(left);
+                if(needs[c - 'a'] > 0) {
+                    windows[c - 'a']--;
+                    if(windows[c - 'a'] < needs[c - 'a']) {
+                        total++;
+                    }
+                }
+                left++;
+            }
+            right++;
+        }
+        return res;
+    }
+}