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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5.     string s;
  6.     cin >> s;
  7.  
  8.     int n = s.size();
  9.  
  10.     int change1 = 0; // BWBWB...
  11.     int change2 = 0; // WBWBW...
  12.  
  13.     for (int i = 0; i < n; i++) {
  14.  
  15.         // Pattern 1: B W B W ...
  16.         char expected1 = (i % 2 == 0) ? 'B' : 'W';
  17.  
  18.         // Pattern 2: W B W B ...
  19.         char expected2 = (i % 2 == 0) ? 'W' : 'B';
  20.  
  21.         if (s[i] != expected1)
  22.             change1++;
  23.  
  24.         if (s[i] != expected2)
  25.             change2++;
  26.     }
  27.  
  28.     cout << min(change1, change2) << endl;
  29.  
  30.     return 0;
  31. }
Success #stdin #stdout 0.01s 5324KB
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stdin
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BBWWB
stdout
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2
https://ideone.com/yS5ru3
language:
C++ (gcc 8.3)
created:
12 hours ago
visibility:
public

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