Codechef Lunchtime 08 Question CHRL2

http://www.codechef.com/problems/CHRL2

Editorial suggests a DP solution in O(n^2)

I was thinking of a different solution.

Obviously , I got a WA.

But I can’t figure out the mistake can anyone help ?

Suppose we store all the occurrences of C,H,E,F seperately.

Then we match each C to the first H which comes after it and then with first E that comes after H and first F that comes after E.

And proceed accordingly.

for eg. in CHHHEEEFFCC

vc -> 0, 9, 10

vh -> 1,2,3

ve -> 4,5,6

vf -> 7,8

now vc[0] = 0;

we can match it with 1(i.e H), 4, and 7

Now vc[1] = 9

There is no i such that vh > 9

Therefore program ends.

Can anyone point out the mistake ?

~Thanks