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  1. #include <iostream>
  2. #include <vector>
  3. #include <map>
  4. #include <algorithm>
  5. #include <string>
  6. using namespace std;
  7.  
  8. #define CASES int t;cin>>t;while(t--)
  9. #define REP(i, val, b) for (int i = val; i < b; ++i)
  10.  
  11. class stringMod
  12. {
  13. public:
  14. 	string s;
  15. 	//Here is the increment frunction.
  16. 	void increment(int pos)
  17. 	{
  18. 		s[pos]++; //We have incremented right most digit by "1"
  19. 		/*
  20. 		When the right most digit is "9" and you are trying to increment it by "1", then that
  21. 		will become ":" in cpp. So we have checked ":" in condition here.
  22. 		*/
  23. 		if (s[pos] == ':')
  24. 		{
  25. 			//First we will make that position to "0".
  26.  
  27. 			//Here is the explanation with example. if the number is 139 and we will do s[2]++. 
  28. 			//Then first it will become "13:". So in this line we will make ":" to "0". 
  29. 			//So our number will become "130".
  30. 			//Now our task is to increment "3" to "4". So we will do increment(pos - 1) here if and only
  31. 			//if pos > 0. Now you must have question in your mind that what is the meaning of the
  32. 			//condition if (pos > 0). So here is the explanation. If our number is 139, then our position
  33. 			//is 2 and we are incrementing our position by 1 so it will become "13:" and after that "130"
  34. 			//and position is 2 so here position is 2 that is greater than 0 so we will increment 
  35. 			//previous position. So we will increment position 2, so our number will become 140. 
  36. 			//Now we are moving towards to else part. When will these condition happen. 
  37. 			//So if we have a number "99" and we have reached to this part and our number 
  38. 			//have became "9:" and then "90". Now here our position is 1 as we have incremented 
  39. 			//last digit so we will increment 0th position, then 
  40. 			//our number will become ":0" and after that our number will become "00" and after that our
  41. 			//position is 0 so we have to prepend "1" to our number so our numbber will become "100". 
  42. 			//and this process will run again. So this is the else part explanation.
  43. 			s[pos] = '0';
  44. 			if (pos > 0)
  45. 			{
  46. 				increment(pos - 1);
  47. 			}
  48. 			else
  49. 			{
  50. 				s.insert(s.begin(), '1');
  51. 			}
  52.  
  53. 		}
  54. 	}
  55. };
  56.  
  57. int main()
  58. {
  59. 	CASES{
  60. 	stringMod s;
  61. 	cin >> s.s;
  62. 	int l = s.s.length(); //length of the input || number
  63.  
  64. 	//First we will increment last digit by "1", 
  65. 	//so that we will check whether the next number is palindrome or not
  66. 	s.increment(l - 1); 
  67. 	l = s.s.length();
  68. 	//As I have explained we will loop through half of the length of input.
  69. 	REP(i, 0, l / 2)
  70. 	{
  71. 		int left = i; //left most digit is this from the input || number
  72. 		int right = (l - 1) - i; //right most digit is thie from input || number
  73. 		//Will run while loop until left and right number is equal as explained
  74. 		while (s.s[left] != s.s[right])
  75. 		{
  76. 			//If not equal we will increment right most number by "1".
  77. 			s.increment(right);
  78. 		}
  79. 	}
  80. 	//Here is the final string.
  81. 	cout << s.s << endl;
  82. }
  83.  
  84. 	return 0;
  85. }
Success #stdin #stdout 0s 4460KB
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https://ideone.com/bUXnNN
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
secret

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