Interpret arbitrary int array as column diagram - pour water over it and output the amount of water that stays on the array. Best Case O(n), Worst Case O(n²), Average Case O(n)

FillUp.cs

fillUp(int[] x){
	int total = 0;
	for(int i = 0;i < x.length-1;i++){
		if(x[i] >= x[i+1]){
			continue; //if neighbor is higher or equal go to next column
		} else {
			int j = 2; //neighbor is known to be lower, so we can start at i+2
			bool pool = false;
			while(i + j < x.length){
				if(x[i+j] >= x[i]){ //as soon as a column is at least as big as the reference column
					pool = true;	//	mark the found pool.
					break;			
				} else{
					j++;
				}
			}
			if(pool){
				int max = x[i] //maximum height of pool
				for(int y = i;y<i+j;y++){
					total += max - x[y]; //fill up
				}
				i += j; //jump over to pool to look for the next one
			}
		}
	}
	Console.WriteLine("Total: " + total);
}