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# Question
Given a sequence of positive integers seq and an integer total, return whether a contiguous sequence of seq sums up to total.
Examples:
[1, 2, 3], 4 # False
[1, 2, 3], 5 # True (because 2 + 3 = 5)
[1, 2, 3], 6 # True (because 1 + 2 + 3 = 6)

////////////////////////////////////////////

  [1,0,3] 0


  // f[i] = sum(sub(i, end))
  // sum(sub(a,b)) = f(b) - f(a)

public boolean isContiguousSum(int[] seq, int sum) {
  if(seq==null) return false;


  for(int i=0; i<seq.length-1; i++){
    int s = 0;
    for(int j=i; j<seq.length-1; j++){
      s += seq[j];
      if (s == sum) return true;
    }
  }
  return false;
}



public boolean isContiguousSum(int[] seq, int sum) {
  if(seq==null) return false;

  int lo=0,hi=1;

  int part = seq[lo];

  while(hi<seq.length-1){
    if(part == sum) return true;
    if(part>sum) {
      part -= seq[lo];
      lo++;
    } else {
      hi++;
      part += seq[hi];
    }
  }

  return false;
}