TC SRM514 div2

Another div2 competition for me, as I am the borderline of div1 and div2.

p250 easy problem, just take diff of x and y, then return sqrt(dx^2+dy^2)

p500 the constraints are small, so just bfs on a large enough grid. maxX, maxY <=30, so you need only a grid of +-60.

p1000 looks daunting, but turns out to be easy, just didn't got scared during SRM. Actually I had 50+ minutes for p1000. Just not that confident. The string concatenation is a disguise, you only need to keep track of length of each element, and number of ones. A trivial DP. Two places need to be careful. One is that the length might get to 50*100=5000 digits, so even long long is not big enough. But you need only the first 15 digits so check that. Another place is my fault, when allocating vector, use max(n+1,K) since n could be smaller than K-1. The first time I got 'uncaught exception' in TC arena yet it runs fine on my own machine.

Another good lesson is to use vec.clear() and vec.resize() to reinitialize to zero. As I was using one[i]+=(s[i]=='1'), the second testcase picks up the old value from testcase 1.