*****************************************************************************
*       www.FindStat.org - The Combinatorial Statistic Finder               *
*                                                                           *
*       Copyright (C) 2019 The FindStatCrew <info@findstat.org>             *
*                                                                           *
*    This information is distributed in the hope that it will be useful,    *
*    but WITHOUT ANY WARRANTY; without even the implied warranty of         *
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.                   *
*****************************************************************************

-----------------------------------------------------------------------------
Statistic identifier: St001355

-----------------------------------------------------------------------------
Collection: Binary words

-----------------------------------------------------------------------------
Description: Number of non-empty prefixes of a binary word that contain equally many 0's and 1's.

Graphically, this is the number of returns to the main diagonal of the monotone lattice path of a binary word.

-----------------------------------------------------------------------------
References: 

-----------------------------------------------------------------------------
Code:
def statistic(P):
    return sum(1 for i in range(2,len(P)+1,2) if P[:i].count(0) == P[:i].count(1) )


-----------------------------------------------------------------------------
Statistic values:

0         => 0
1         => 0
00        => 0
01        => 1
10        => 1
11        => 0
000       => 0
001       => 0
010       => 1
011       => 1
100       => 1
101       => 1
110       => 0
111       => 0
0000      => 0
0001      => 0
0010      => 0
0011      => 1
0100      => 1
0101      => 2
0110      => 2
0111      => 1
1000      => 1
1001      => 2
1010      => 2
1011      => 1
1100      => 1
1101      => 0
1110      => 0
1111      => 0
00000     => 0
00001     => 0
00010     => 0
00011     => 0
00100     => 0
00101     => 0
00110     => 1
00111     => 1
01000     => 1
01001     => 1
01010     => 2
01011     => 2
01100     => 2
01101     => 2
01110     => 1
01111     => 1
10000     => 1
10001     => 1
10010     => 2
10011     => 2
10100     => 2
10101     => 2
10110     => 1
10111     => 1
11000     => 1
11001     => 1
11010     => 0
11011     => 0
11100     => 0
11101     => 0
11110     => 0
11111     => 0
000000    => 0
000001    => 0
000010    => 0
000011    => 0
000100    => 0
000101    => 0
000110    => 0
000111    => 1
001000    => 0
001001    => 0
001010    => 0
001011    => 1
001100    => 1
001101    => 2
001110    => 2
001111    => 1
010000    => 1
010001    => 1
010010    => 1
010011    => 2
010100    => 2
010101    => 3
010110    => 3
010111    => 2
011000    => 2
011001    => 3
011010    => 3
011011    => 2
011100    => 2
011101    => 1
011110    => 1
011111    => 1
100000    => 1
100001    => 1
100010    => 1
100011    => 2
100100    => 2
100101    => 3
100110    => 3
100111    => 2
101000    => 2
101001    => 3
101010    => 3
101011    => 2
101100    => 2
101101    => 1
101110    => 1
101111    => 1
110000    => 1
110001    => 2
110010    => 2
110011    => 1
110100    => 1
110101    => 0
110110    => 0
110111    => 0
111000    => 1
111001    => 0
111010    => 0
111011    => 0
111100    => 0
111101    => 0
111110    => 0
111111    => 0
0000000   => 0
0000001   => 0
0000010   => 0
0000011   => 0
0000100   => 0
0000101   => 0
0000110   => 0
0000111   => 0
0001000   => 0
0001001   => 0
0001010   => 0
0001011   => 0
0001100   => 0
0001101   => 0
0001110   => 1
0001111   => 1
0010000   => 0
0010001   => 0
0010010   => 0
0010011   => 0
0010100   => 0
0010101   => 0
0010110   => 1
0010111   => 1
0011000   => 1
0011001   => 1
0011010   => 2
0011011   => 2
0011100   => 2
0011101   => 2
0011110   => 1
0011111   => 1
0100000   => 1
0100001   => 1
0100010   => 1
0100011   => 1
0100100   => 1
0100101   => 1
0100110   => 2
0100111   => 2
0101000   => 2
0101001   => 2
0101010   => 3
0101011   => 3
0101100   => 3
0101101   => 3
0101110   => 2
0101111   => 2
0110000   => 2
0110001   => 2
0110010   => 3
0110011   => 3
0110100   => 3
0110101   => 3
0110110   => 2
0110111   => 2
0111000   => 2
0111001   => 2
0111010   => 1
0111011   => 1
0111100   => 1
0111101   => 1
0111110   => 1
0111111   => 1
1000000   => 1
1000001   => 1
1000010   => 1
1000011   => 1
1000100   => 1
1000101   => 1
1000110   => 2
1000111   => 2
1001000   => 2
1001001   => 2
1001010   => 3
1001011   => 3
1001100   => 3
1001101   => 3
1001110   => 2
1001111   => 2
1010000   => 2
1010001   => 2
1010010   => 3
1010011   => 3
1010100   => 3
1010101   => 3
1010110   => 2
1010111   => 2
1011000   => 2
1011001   => 2
1011010   => 1
1011011   => 1
1011100   => 1
1011101   => 1
1011110   => 1
1011111   => 1
1100000   => 1
1100001   => 1
1100010   => 2
1100011   => 2
1100100   => 2
1100101   => 2
1100110   => 1
1100111   => 1
1101000   => 1
1101001   => 1
1101010   => 0
1101011   => 0
1101100   => 0
1101101   => 0
1101110   => 0
1101111   => 0
1110000   => 1
1110001   => 1
1110010   => 0
1110011   => 0
1110100   => 0
1110101   => 0
1110110   => 0
1110111   => 0
1111000   => 0
1111001   => 0
1111010   => 0
1111011   => 0
1111100   => 0
1111101   => 0
1111110   => 0
1111111   => 0
00000000  => 0
00000001  => 0
00000010  => 0
00000011  => 0
00000100  => 0
00000101  => 0
00000110  => 0
00000111  => 0
00001000  => 0
00001001  => 0
00001010  => 0
00001011  => 0
00001100  => 0
00001101  => 0
00001110  => 0
00001111  => 1
00010000  => 0
00010001  => 0
00010010  => 0
00010011  => 0
00010100  => 0
00010101  => 0
00010110  => 0
00010111  => 1
00011000  => 0
00011001  => 0
00011010  => 0
00011011  => 1
00011100  => 1
00011101  => 2
00011110  => 2
00011111  => 1
00100000  => 0
00100001  => 0
00100010  => 0
00100011  => 0
00100100  => 0
00100101  => 0
00100110  => 0
00100111  => 1
00101000  => 0
00101001  => 0
00101010  => 0
00101011  => 1
00101100  => 1
00101101  => 2
00101110  => 2
00101111  => 1
00110000  => 1
00110001  => 1
00110010  => 1
00110011  => 2
00110100  => 2
00110101  => 3
00110110  => 3
00110111  => 2
00111000  => 2
00111001  => 3
00111010  => 3
00111011  => 2
00111100  => 2
00111101  => 1
00111110  => 1
00111111  => 1
01000000  => 1
01000001  => 1
01000010  => 1
01000011  => 1
01000100  => 1
01000101  => 1
01000110  => 1
01000111  => 2
01001000  => 1
01001001  => 1
01001010  => 1
01001011  => 2
01001100  => 2
01001101  => 3
01001110  => 3
01001111  => 2
01010000  => 2
01010001  => 2
01010010  => 2
01010011  => 3
01010100  => 3
01010101  => 4
01010110  => 4
01010111  => 3
01011000  => 3
01011001  => 4
01011010  => 4
01011011  => 3
01011100  => 3
01011101  => 2
01011110  => 2
01011111  => 2
01100000  => 2
01100001  => 2
01100010  => 2
01100011  => 3
01100100  => 3
01100101  => 4
01100110  => 4
01100111  => 3
01101000  => 3
01101001  => 4
01101010  => 4
01101011  => 3
01101100  => 3
01101101  => 2
01101110  => 2
01101111  => 2
01110000  => 2
01110001  => 3
01110010  => 3
01110011  => 2
01110100  => 2
01110101  => 1
01110110  => 1
01110111  => 1
01111000  => 2
01111001  => 1
01111010  => 1
01111011  => 1
01111100  => 1
01111101  => 1
01111110  => 1
01111111  => 1
10000000  => 1
10000001  => 1
10000010  => 1
10000011  => 1
10000100  => 1
10000101  => 1
10000110  => 1
10000111  => 2
10001000  => 1
10001001  => 1
10001010  => 1
10001011  => 2
10001100  => 2
10001101  => 3
10001110  => 3
10001111  => 2
10010000  => 2
10010001  => 2
10010010  => 2
10010011  => 3
10010100  => 3
10010101  => 4
10010110  => 4
10010111  => 3
10011000  => 3
10011001  => 4
10011010  => 4
10011011  => 3
10011100  => 3
10011101  => 2
10011110  => 2
10011111  => 2
10100000  => 2
10100001  => 2
10100010  => 2
10100011  => 3
10100100  => 3
10100101  => 4
10100110  => 4
10100111  => 3
10101000  => 3
10101001  => 4
10101010  => 4
10101011  => 3
10101100  => 3
10101101  => 2
10101110  => 2
10101111  => 2
10110000  => 2
10110001  => 3
10110010  => 3
10110011  => 2
10110100  => 2
10110101  => 1
10110110  => 1
10110111  => 1
10111000  => 2
10111001  => 1
10111010  => 1
10111011  => 1
10111100  => 1
10111101  => 1
10111110  => 1
10111111  => 1
11000000  => 1
11000001  => 1
11000010  => 1
11000011  => 2
11000100  => 2
11000101  => 3
11000110  => 3
11000111  => 2
11001000  => 2
11001001  => 3
11001010  => 3
11001011  => 2
11001100  => 2
11001101  => 1
11001110  => 1
11001111  => 1
11010000  => 1
11010001  => 2
11010010  => 2
11010011  => 1
11010100  => 1
11010101  => 0
11010110  => 0
11010111  => 0
11011000  => 1
11011001  => 0
11011010  => 0
11011011  => 0
11011100  => 0
11011101  => 0
11011110  => 0
11011111  => 0
11100000  => 1
11100001  => 2
11100010  => 2
11100011  => 1
11100100  => 1
11100101  => 0
11100110  => 0
11100111  => 0
11101000  => 1
11101001  => 0
11101010  => 0
11101011  => 0
11101100  => 0
11101101  => 0
11101110  => 0
11101111  => 0
11110000  => 1
11110001  => 0
11110010  => 0
11110011  => 0
11110100  => 0
11110101  => 0
11110110  => 0
11110111  => 0
11111000  => 0
11111001  => 0
11111010  => 0
11111011  => 0
11111100  => 0
11111101  => 0
11111110  => 0
11111111  => 0
000000000 => 0
000000001 => 0
000000010 => 0
000000011 => 0
000000100 => 0
000000101 => 0
000000110 => 0
000000111 => 0
000001000 => 0
000001001 => 0
000001010 => 0
000001011 => 0
000001100 => 0
000001101 => 0
000001110 => 0
000001111 => 0
000010000 => 0
000010001 => 0
000010010 => 0
000010011 => 0
000010100 => 0
000010101 => 0
000010110 => 0
000010111 => 0
000011000 => 0
000011001 => 0
000011010 => 0
000011011 => 0
000011100 => 0
000011101 => 0
000011110 => 1
000011111 => 1
000100000 => 0
000100001 => 0
000100010 => 0
000100011 => 0
000100100 => 0
000100101 => 0
000100110 => 0
000100111 => 0
000101000 => 0
000101001 => 0
000101010 => 0
000101011 => 0
000101100 => 0
000101101 => 0
000101110 => 1
000101111 => 1
000110000 => 0
000110001 => 0
000110010 => 0
000110011 => 0
000110100 => 0
000110101 => 0
000110110 => 1
000110111 => 1
000111000 => 1
000111001 => 1
000111010 => 2
000111011 => 2
000111100 => 2
000111101 => 2
000111110 => 1
000111111 => 1
001000000 => 0
001000001 => 0
001000010 => 0
001000011 => 0
001000100 => 0
001000101 => 0
001000110 => 0
001000111 => 0
001001000 => 0
001001001 => 0
001001010 => 0
001001011 => 0
001001100 => 0
001001101 => 0
001001110 => 1
001001111 => 1
001010000 => 0
001010001 => 0
001010010 => 0
001010011 => 0
001010100 => 0
001010101 => 0
001010110 => 1
001010111 => 1
001011000 => 1
001011001 => 1
001011010 => 2
001011011 => 2
001011100 => 2
001011101 => 2
001011110 => 1
001011111 => 1
001100000 => 1
001100001 => 1
001100010 => 1
001100011 => 1
001100100 => 1
001100101 => 1
001100110 => 2
001100111 => 2
001101000 => 2
001101001 => 2
001101010 => 3
001101011 => 3
001101100 => 3
001101101 => 3
001101110 => 2
001101111 => 2
001110000 => 2
001110001 => 2
001110010 => 3
001110011 => 3
001110100 => 3
001110101 => 3
001110110 => 2
001110111 => 2
001111000 => 2
001111001 => 2
001111010 => 1
001111011 => 1
001111100 => 1
001111101 => 1
001111110 => 1
001111111 => 1
010000000 => 1
010000001 => 1
010000010 => 1
010000011 => 1
010000100 => 1
010000101 => 1
010000110 => 1
010000111 => 1
010001000 => 1
010001001 => 1
010001010 => 1
010001011 => 1
010001100 => 1
010001101 => 1
010001110 => 2
010001111 => 2
010010000 => 1
010010001 => 1
010010010 => 1
010010011 => 1
010010100 => 1
010010101 => 1
010010110 => 2
010010111 => 2
010011000 => 2
010011001 => 2
010011010 => 3
010011011 => 3
010011100 => 3
010011101 => 3
010011110 => 2
010011111 => 2
010100000 => 2
010100001 => 2
010100010 => 2
010100011 => 2
010100100 => 2
010100101 => 2
010100110 => 3
010100111 => 3
010101000 => 3
010101001 => 3
010101010 => 4
010101011 => 4
010101100 => 4
010101101 => 4
010101110 => 3
010101111 => 3
010110000 => 3
010110001 => 3
010110010 => 4
010110011 => 4
010110100 => 4
010110101 => 4
010110110 => 3
010110111 => 3
010111000 => 3
010111001 => 3
010111010 => 2
010111011 => 2
010111100 => 2
010111101 => 2
010111110 => 2
010111111 => 2
011000000 => 2
011000001 => 2
011000010 => 2
011000011 => 2
011000100 => 2
011000101 => 2
011000110 => 3
011000111 => 3
011001000 => 3
011001001 => 3
011001010 => 4
011001011 => 4
011001100 => 4
011001101 => 4
011001110 => 3
011001111 => 3
011010000 => 3
011010001 => 3
011010010 => 4
011010011 => 4
011010100 => 4
011010101 => 4
011010110 => 3
011010111 => 3
011011000 => 3
011011001 => 3
011011010 => 2
011011011 => 2
011011100 => 2
011011101 => 2
011011110 => 2
011011111 => 2
011100000 => 2
011100001 => 2
011100010 => 3
011100011 => 3
011100100 => 3
011100101 => 3
011100110 => 2
011100111 => 2
011101000 => 2
011101001 => 2
011101010 => 1
011101011 => 1
011101100 => 1
011101101 => 1
011101110 => 1
011101111 => 1
011110000 => 2
011110001 => 2
011110010 => 1
011110011 => 1
011110100 => 1
011110101 => 1
011110110 => 1
011110111 => 1
011111000 => 1
011111001 => 1
011111010 => 1
011111011 => 1
011111100 => 1
011111101 => 1
011111110 => 1
011111111 => 1
100000000 => 1
100000001 => 1
100000010 => 1
100000011 => 1
100000100 => 1
100000101 => 1
100000110 => 1
100000111 => 1
100001000 => 1
100001001 => 1
100001010 => 1
100001011 => 1
100001100 => 1
100001101 => 1
100001110 => 2
100001111 => 2
100010000 => 1
100010001 => 1
100010010 => 1
100010011 => 1
100010100 => 1
100010101 => 1
100010110 => 2
100010111 => 2
100011000 => 2
100011001 => 2
100011010 => 3
100011011 => 3
100011100 => 3
100011101 => 3
100011110 => 2
100011111 => 2
100100000 => 2
100100001 => 2
100100010 => 2
100100011 => 2
100100100 => 2
100100101 => 2
100100110 => 3
100100111 => 3
100101000 => 3
100101001 => 3
100101010 => 4
100101011 => 4
100101100 => 4
100101101 => 4
100101110 => 3
100101111 => 3
100110000 => 3
100110001 => 3
100110010 => 4
100110011 => 4
100110100 => 4
100110101 => 4
100110110 => 3
100110111 => 3
100111000 => 3
100111001 => 3
100111010 => 2
100111011 => 2
100111100 => 2
100111101 => 2
100111110 => 2
100111111 => 2
101000000 => 2
101000001 => 2
101000010 => 2
101000011 => 2
101000100 => 2
101000101 => 2
101000110 => 3
101000111 => 3
101001000 => 3
101001001 => 3
101001010 => 4
101001011 => 4
101001100 => 4
101001101 => 4
101001110 => 3
101001111 => 3
101010000 => 3
101010001 => 3
101010010 => 4
101010011 => 4
101010100 => 4
101010101 => 4
101010110 => 3
101010111 => 3
101011000 => 3
101011001 => 3
101011010 => 2
101011011 => 2
101011100 => 2
101011101 => 2
101011110 => 2
101011111 => 2
101100000 => 2
101100001 => 2
101100010 => 3
101100011 => 3
101100100 => 3
101100101 => 3
101100110 => 2
101100111 => 2
101101000 => 2
101101001 => 2
101101010 => 1
101101011 => 1
101101100 => 1
101101101 => 1
101101110 => 1
101101111 => 1
101110000 => 2
101110001 => 2
101110010 => 1
101110011 => 1
101110100 => 1
101110101 => 1
101110110 => 1
101110111 => 1
101111000 => 1
101111001 => 1
101111010 => 1
101111011 => 1
101111100 => 1
101111101 => 1
101111110 => 1
101111111 => 1
110000000 => 1
110000001 => 1
110000010 => 1
110000011 => 1
110000100 => 1
110000101 => 1
110000110 => 2
110000111 => 2
110001000 => 2
110001001 => 2
110001010 => 3
110001011 => 3
110001100 => 3
110001101 => 3
110001110 => 2
110001111 => 2
110010000 => 2
110010001 => 2
110010010 => 3
110010011 => 3
110010100 => 3
110010101 => 3
110010110 => 2
110010111 => 2
110011000 => 2
110011001 => 2
110011010 => 1
110011011 => 1
110011100 => 1
110011101 => 1
110011110 => 1
110011111 => 1
110100000 => 1
110100001 => 1
110100010 => 2
110100011 => 2
110100100 => 2
110100101 => 2
110100110 => 1
110100111 => 1
110101000 => 1
110101001 => 1
110101010 => 0
110101011 => 0
110101100 => 0
110101101 => 0
110101110 => 0
110101111 => 0
110110000 => 1
110110001 => 1
110110010 => 0
110110011 => 0
110110100 => 0
110110101 => 0
110110110 => 0
110110111 => 0
110111000 => 0
110111001 => 0
110111010 => 0
110111011 => 0
110111100 => 0
110111101 => 0
110111110 => 0
110111111 => 0
111000000 => 1
111000001 => 1
111000010 => 2
111000011 => 2
111000100 => 2
111000101 => 2
111000110 => 1
111000111 => 1
111001000 => 1
111001001 => 1
111001010 => 0
111001011 => 0
111001100 => 0
111001101 => 0
111001110 => 0
111001111 => 0
111010000 => 1
111010001 => 1
111010010 => 0
111010011 => 0
111010100 => 0
111010101 => 0
111010110 => 0
111010111 => 0
111011000 => 0
111011001 => 0
111011010 => 0
111011011 => 0
111011100 => 0
111011101 => 0
111011110 => 0
111011111 => 0
111100000 => 1
111100001 => 1
111100010 => 0
111100011 => 0
111100100 => 0
111100101 => 0
111100110 => 0
111100111 => 0
111101000 => 0
111101001 => 0
111101010 => 0
111101011 => 0
111101100 => 0
111101101 => 0
111101110 => 0
111101111 => 0
111110000 => 0
111110001 => 0
111110010 => 0
111110011 => 0
111110100 => 0
111110101 => 0
111110110 => 0
111110111 => 0
111111000 => 0
111111001 => 0
111111010 => 0
111111011 => 0
111111100 => 0
111111101 => 0
111111110 => 0
111111111 => 0

-----------------------------------------------------------------------------
Created: Feb 11, 2019 at 18:21 by Christian Stump

-----------------------------------------------------------------------------
Last Updated: Feb 12, 2019 at 07:43 by Christian Stump