Given a string of brackets, the task is to find an index k which decides the number of opening brackets is equal to the number of closing brackets.
String must be consists of only opening and closing brackets i.e. ‘(‘ and ‘)’.
An equal point is an index such that the number of opening brackets before it is equal to the number of closing brackets from and after.
Examples:
Input : str = "(())))(" Output: 4 After index 4, string splits into (()) and ))(. Number of opening brackets in the first part is equal to number of closing brackets in the second part. Input : str = "))" Output: 2 As after 2nd position i.e. )) and "empty" string will be split into these two parts: So, in this number of opening brackets i.e. 0 in the first part is equal to number of closing brackets in the second part i.e. also 0.
Asked in : Amazon
- Store the number of opening brackets appears in the string up to every index, it must start from starting index.
- Similarly, Store the number of closing brackets appears in the string upto each and every index but it should be done from last index.
- Check if any index has the same value of opening and closing brackets.
C++
// C++ program to find an index k which // decides the number of opening brackets // is equal to the number of closing brackets #include<bits/stdc++.h> using namespace std; // Function to find an equal index int findIndex(string str) { int len = str.length(); int open[len+1], close[len+1]; int index = -1; memset (open, 0, sizeof (open)); memset (close, 0, sizeof (close)); open[0] = 0; close[len] = 0; if (str[0]== '(' ) open[1] = 1; if (str[len-1] == ')' ) close[len-1] = 1; // Store the number of opening brackets // at each index for ( int i = 1; i < len; i++) { if ( str[i] == '(' ) open[i+1] = open[i] + 1; else open[i+1] = open[i]; } // Store the number of closing brackets // at each index for ( int i = len-2; i >= 0; i--) { if ( str[i] == ')' ) close[i] = close[i+1] + 1; else close[i] = close[i+1]; } // check if there is no opening or closing // brackets if (open[len] == 0) return len; if (close[0] == 0) return 0; // check if there is any index at which // both brackets are equal for ( int i=0; i<=len; i++) if (open[i] == close[i]) index = i; return index; } // Driver code int main() { string str = "(()))(()()())))" ; cout << findIndex(str); return 0; } |
Java
// Java program to find an index k which // decides the number of opening brackets // is equal to the number of closing brackets public class GFG { // Method to find an equal index static int findIndex(String str) { int len = str.length(); int open[] = new int [len+ 1 ]; int close[] = new int [len+ 1 ]; int index = - 1 ; open[ 0 ] = 0 ; close[len] = 0 ; if (str.charAt( 0 )== '(' ) open[ 1 ] = 1 ; if (str.charAt(len- 1 ) == ')' ) close[len- 1 ] = 1 ; // Store the number of opening brackets // at each index for ( int i = 1 ; i < len; i++) { if ( str.charAt(i) == '(' ) open[i+ 1 ] = open[i] + 1 ; else open[i+ 1 ] = open[i]; } // Store the number of closing brackets // at each index for ( int i = len- 2 ; i >= 0 ; i--) { if ( str.charAt(i) == ')' ) close[i] = close[i+ 1 ] + 1 ; else close[i] = close[i+ 1 ]; } // check if there is no opening or closing // brackets if (open[len] == 0 ) return len; if (close[ 0 ] == 0 ) return 0 ; // check if there is any index at which // both brackets are equal for ( int i= 0 ; i<=len; i++) if (open[i] == close[i]) index = i; return index; } // Driver Method public static void main(String[] args) { String str = "(()))(()()())))" ; System.out.println(findIndex(str)); } } |
Python 3
# Method to find an equal index def findIndex( str ): l = len ( str ) open = [ 0 ] * (l + 1 ) close = [ 0 ] * (l + 1 ) index = - 1 open [ 0 ] = 0 close[l] = 0 if ( str [ 0 ] = = '(' ): open [ 1 ] = 1 if ( str [l - 1 ] = = ')' ): close[l - 1 ] = 1 # Store the number of # opening brackets # at each index for i in range ( 1 , l): if ( str [i] = = '(' ): open [i + 1 ] = open [i] + 1 else : open [i + 1 ] = open [i] # Store the number # of closing brackets # at each index for i in range (l - 2 , - 1 , - 1 ): if ( str [i] = = ')' ): close[i] = close[i + 1 ] + 1 else : close[i] = close[i + 1 ] # check if there is no # opening or closing brackets if ( open [l] = = 0 ): return len if (close[ 0 ] = = 0 ): return 0 # check if there is any # index at which both # brackets are equal for i in range (l + 1 ): if ( open [i] = = close[i]): index = i return index # Driver Code str = "(()))(()()())))" print (findIndex( str )) # This code is contributed # by ChitraNayal |
C#
// C# program to find an index // k which decides the number // of opening brackets is equal // to the number of closing brackets using System; class GFG { // Method to find an equal index static int findIndex( string str) { int len = str.Length; int [] open = new int [len + 1]; int [] close = new int [len + 1]; int index = -1; open[0] = 0; close[len] = 0; if (str[0] == '(' ) open[1] = 1; if (str[len - 1] == ')' ) close[len - 1] = 1; // Store the number of // opening brackets // at each index for ( int i = 1; i < len; i++) { if (str[i] == '(' ) open[i + 1] = open[i] + 1; else open[i + 1] = open[i]; } // Store the number // of closing brackets // at each index for ( int i = len - 2; i >= 0; i--) { if (str[i] == ')' ) close[i] = close[i + 1] + 1; else close[i] = close[i + 1]; } // check if there is no // opening or closing // brackets if (open[len] == 0) return len; if (close[0] == 0) return 0; // check if there is any // index at which both // brackets are equal for ( int i = 0; i <= len; i++) if (open[i] == close[i]) index = i; return index; } // Driver Code public static void Main() { string str = "(()))(()()())))" ; Console.Write(findIndex(str)); } } // This code is contributed // by ChitraNayal |
PHP
<?php // Method to find an equal index function findIndex( $str ) { $len = strlen ( $str ); $open = array (0, $len + 1, NULL); $close = array (0, $len + 1, NULL); $index = -1; $open [0] = 0; $close [ $len ] = 0; if ( $str [0] == '(' ) $open [1] = 1; if ( $str [ $len - 1] == ')' ) $close [ $len - 1] = 1; // Store the number // of opening brackets // at each index for ( $i = 1; $i < $len ; $i ++) { if ( $str [ $i ] == '(' ) $open [ $i + 1] = $open [ $i ] + 1; else $open [ $i + 1] = $open [ $i ]; } // Store the number // of closing brackets // at each index for ( $i = $len - 2; $i >= 0; $i --) { if ( $str [ $i ] == ')' ) $close [ $i ] = $close [ $i + 1] + 1; else $close [ $i ] = $close [ $i + 1]; } // check if there is no // opening or closing // brackets if ( $open [ $len ] == 0) return $len ; if ( $close [0] == 0) return 0; // check if there is any // index at which both // brackets are equal for ( $i = 0; $i <= $len ; $i ++) if ( $open [ $i ] == $close [ $i ]) $index = $i ; return $index ; } // Driver Code $str = "(()))(()()())))" ; echo (findIndex( $str )); // This code is contributed // by ChitraNayal ?> |
Output:
9
Time Complexity : O(n)
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