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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. long long solve(const string& s1, const string& s2) {
  5.     int n = s1.size();
  6.  
  7.     // count total potholes
  8.     long long total = 0;
  9.     for (int i = 0; i < n; i++) {
  10.         total += (s1[i] == 'x') + (s2[i] == 'x');
  11.     }
  12.  
  13.     auto w = [&](int row, int col) {
  14.         return (row == 0 ? s1[col] : s2[col]) == 'x' ? 1 : 0;
  15.     };
  16.  
  17.     // dp[row] = min potholes missed to reach this row at current col
  18.     long long dp0 = w(0, 0);
  19.     long long dp1 = w(1, 0);
  20.  
  21.     for (int i = 0; i < n; i++) {
  22.         // try switching lanes at current column
  23.         long long new0 = min(dp0, dp1 + w(0, i));
  24.         long long new1 = min(dp1, dp0 + w(1, i));
  25.         dp0 = new0;
  26.         dp1 = new1;
  27.  
  28.         if (i == n - 1) break;
  29.  
  30.         // move to next column
  31.         dp0 += w(0, i + 1);
  32.         dp1 += w(1, i + 1);
  33.     }
  34.  
  35.     return total - min(dp0, dp1);
  36. }
  37.  
  38. int main() {
  39.     ios::sync_with_stdio(false);
  40.     cin.tie(nullptr);
  41.  
  42.     string s1, s2;
  43.     cin >> s1 >> s2;
  44.  
  45.     cout << solve(s1, s2) << "\n";
  46.     return 0;
  47. }
Success #stdin #stdout 0.01s 5284KB
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stdin 
Standard input is empty
stdout 
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https://ideone.com/O2crgY
language:
C++14 (gcc 8.3)
created:
12 hours ago
visibility:
public

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