Create 828.Count-Unique-Characters-of-All-Substrings-of-a-Given-Strin…

…g_v2.cpp

Hash/828.Count-Unique-Characters-of-All-Substrings-of-a-Given-String/828.Count-Unique-Characters-of-All-Substrings-of-a-Given-String_v2.cpp

@@ -0,0 +1,24 @@
+class Solution {
+public:
+    int uniqueLetterString(string s) 
+    {
+        int n = s.size();
+        vector<vector<int>>pos(26); 
+
+        for (int k=0; k<26; k++)
+            pos[k].push_back(-1);
+        for (int i=0; i<n; i++)    
+            pos[s[i]-'A'].push_back(i);
+        for (int i=0; i<n; i++)    
+            pos[s[i]-'A'].push_back(n);
+
+        int ret = 0;
+        for (int k=0; k<26; k++)
+            for (int i=1; i<pos[k].size()-1; i++)
+            {
+                ret += (pos[k][i]-pos[k][i-1])*(pos[k][i+1]-pos[k][i]);
+            }
+
+        return ret;    
+    }
+};