cassidoo challenge 25-06-2018

cassidoo challenge 25-06-2018

/*
Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.

Example:
waterTrap([2,0,2])
> 2
Structure is like this:
| |
|_|

waterTrap({3, 0, 0, 2, 0, 4})
>10
Structure is like this:
     |
|    |
|  | |
|__|_|
(We can trap 6 units of water between 3 and 2, 1 unit on top of bar 2, and 3 units between 2
and 4)

*/

function waterTrap(structure) {
   if (structure.length<=1) {
      return(0);
   }
   else {
      // anotar altura de la primera barra
      var leftHeight=structure[0];
      // buscar la siguiente barra más alta o igual que la primera
      var i=1;
      while ((i<structure.length) && (structure[i]<leftHeight)) {
         i++;
      }
      // calcular el volumen entre esas dos barras
      var waterRectangleHeight=structure[i];
      if (leftHeight<=structure[i]) {
         waterRectangleHeight=leftHeight;
      }

      var subTotalWater=waterRectangleHeight*(i-1);
      for (j=1;j<i;j++){
         subTotalWater=subTotalWater-structure[j];
      }
      // sumarle el volumen del resto de la estructura a la derecha (llamada recursiva)
      return(subTotalWater + waterTrap(structure.slice(i,structure.length+1)));
   }
}
console.log(waterTrap([])); // result: 0
console.log(waterTrap([5])); // result: 0
console.log(waterTrap([2,0,2])); // result: 2
console.log(waterTrap([3, 0, 0, 2, 0, 4])); // result: 10