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  1. /* package whatever; // don't place package name! */
  2.  
  3.  
  4. class CountLongestBalanced {
  5.     public static void main(String[] args) {
  6.         String[] testCases = {"(()", ")()())", "((()()", "((()(()()", "(())(()", "())()()"};
  7.         for (String s : testCases) {
  8.             System.out.printf("%s -> %d\n", s, countLongestBalanced(s, 0));
  9.         }
  10.     }
  11.  
  12.     static int countLongestBalanced(String str, int start) {
  13.         if ((str.length() - start)  <= 1) return 0;
  14.         int longestN = 0;
  15.         int curN = 0;
  16.         int count = 0;
  17.         int lastRunStart = 0;
  18.         for (int i = start; i < str.length(); ++i) {
  19.             switch(str.charAt(i)) {
  20.                 case '(': ++count; break;
  21.                 case ')': --count; break;
  22.                 default: continue;
  23.             }
  24.             ++curN;
  25.             if (count == 0) {
  26.                 longestN = Math.max(curN, longestN);
  27.                 lastRunStart = i + 1;
  28.             } else if (count < 0) {
  29.                 //bad balance, start over
  30.                 curN = 0;
  31.                 count = 0;
  32.                 lastRunStart = i + 1;
  33.             }
  34.         }
  35.         if (count == 0) longestN = Math.max(curN, longestN);
  36.         else if (count > 0) { //"save" unbalance for extra open pars by skipping them
  37.             int i = lastRunStart;
  38.             for (; i < str.length() && count > 0; ++i) {
  39.                 if (str.charAt(i) == '(') --count;
  40.                 else if (str.charAt(i) == ')') ++count;
  41.             }
  42.             if (i < str.length()) {
  43.             	//Note: this will be called only once (no deeper recursion)
  44.                 longestN = Math.max(longestN, countLongestBalanced(str, i));
  45.             }
  46.         }
  47.         return longestN;
  48.     }
  49. }
Success #stdin #stdout 0.1s 320512KB
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Standard input is empty
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(() -> 2
)()()) -> 4
((()() -> 4
((()(()() -> 4
(())(() -> 4
())()() -> 4
https://ideone.com/v2ST3z
language:
Java (HotSpot 12)
created:
8 years ago
visibility:
public

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