Create 3714.Longest-Balanced-Substring-II.cpp

Author: wisdompeak

Hash/3714.Longest-Balanced-Substring-II/3714.Longest-Balanced-Substring-II.cpp

@@ -0,0 +1,63 @@
+class Solution {
+public:
+    int longestBalanced(string s) {
+        int n = s.size();
+        int best = 0;
+
+        int run = 1;
+        for (int i=1; i<n; i++) {
+            if (s[i]==s[i-1]) 
+                run++;
+            else {
+                best = max(best, run);
+                run = 1;
+            }                
+        }
+        best = max(best, run);
+
+        for (char skip: {'a','b','c'}) {
+            int i = 0;
+            while (i<n) {
+                while (i<n && s[i]==skip) i++;
+                if (i>=n) break;
+                int j = i;
+                while (j<n && s[j]!=skip) j++;
+
+                if (j-i>=2) {
+                    unordered_map<int,int>first;
+                    first[0] = i-1;
+                    int diff = 0;
+                    char c1 = s[i];
+                    for (int k=i; k<j; k++) {
+                        if (s[k]==c1) diff++;
+                        else diff--;
+                        if (first.find(diff)!=first.end()) {
+                            int len = k-first[diff];                            
+                            best = max(best, len);
+                        } else {
+                            first[diff] = k;
+                        }
+                    }
+                }
+                i = j;
+            }            
+        }
+
+        map<pair<int,int>, int>Map;
+        Map[{0,0}] = -1;
+        int ca=0, cb=0, cc=0;
+        for (int i=0; i<n; i++) {
+            if (s[i]=='a') ca++;
+            else if (s[i]=='b') cb++;
+            else cc++;
+            if (Map.find({ca-cb, ca-cc})!=Map.end()) {
+                int len = i - Map[{ca-cb,ca-cc}];
+                best = max(best, len);
+            } else {
+                Map[{ca-cb,ca-cc}] = i;
+            }
+        }
+
+        return best;
+    }
+};