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  1. #include <iostream>
  2. #include <vector>
  3.  
  4. using namespace std;
  5. // created a function of vector of integers 'height' and it returns the amout of water trapped 
  6. int trap(vector<int> & height){
  7. 	if(height.empty())
  8. 	return 0;
  9.  
  10. 	// created 2 pointers : 'left', 'right'
  11. 	// initializing the left and left so that we can track left and right pointers
  12. 	int left = 0, right = height.size() - 1;
  13. 	//also initialized max_left, max_right and the amout of water trapped 
  14.     int max_left = 0, max_right = 0;
  15.     int water_trapped = 0;
  16.  
  17.     //now while loop will run until the left pointer is less than or equal to the right pointer 
  18.     while (left <= right) {
  19.         if (height[left] <= height[right]) {
  20.         	//left side height is greater than max_left
  21.             if (height[left] > max_left)
  22.             // update it to the current height 
  23.                 max_left = height[left];
  24.             else
  25.             // we are calculating the water trapped 
  26.                 water_trapped += max_left - height[left];
  27.             left++;
  28.         } else {
  29.         	// same thing as we did above we are again doing it if we are processing from the right hand side 
  30.             if (height[right] > max_right)
  31.                 max_right = height[right];
  32.             else
  33.                 water_trapped += max_right - height[right];
  34.             right--;
  35.         }
  36.     }
  37.     return water_trapped;
  38. }
  39.  
  40. int main(){
  41.      // in the main func we are simply passing the values 
  42. 	vector<int> height = {3,1,2,4,0,2,1,3};
  43. 	// after initializing we passed to the trap func and printing the output using cout func
  44.     cout << trap(height) << "\n";
  45.     return 0;
  46. }
  47.  
Success #stdin #stdout 0.01s 5280KB
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stdin 
Standard input is empty
stdout 
9
https://ideone.com/MHdkRx
language:
C++14 (gcc 8.3)
created:
15 days ago
visibility:
public

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