Create 1371. Find the Longest Substring Containing Vowels in Even Counts

1371. Find the Longest Substring Containing Vowels in Even Counts

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+
+class Solution {
+public:
+    map<char,int> s = {{'a',0},{'e',1},{'i',2},{'o',3},{'u',4}};
+
+    int findTheLongestSubstring(string str) {
+        int mask=0;
+        vector<int> pre;
+        for(auto e : str){
+            if(s.find(e) != s.end()){
+                mask = mask ^ (1<<(e-'a'));
+            }
+            pre.push_back(mask);
+        }
+
+        // for(auto e : pre) cout << e << " ";
+
+        map<int,int> m; m[0] = -1;
+        int ans=0;
+        for(int i=0; i<pre.size(); i++){
+            auto e = pre[i];
+            if(m.find(e) == m.end()){
+                m[e] = i;
+            }
+
+            ans = max(ans, i-m[e]);
+        }
+
+        return ans;
+    }
+};
+
+
+// xor
+// bit unchagned
+// 0 0 0
+// 1 0 1
+// bit flip 
+// 0 1 1
+// 1 1 0