### mostafaabdelaal_03's blog

By mostafaabdelaal_03, history, 3 months ago,
[D. Min Cost String](https://codeforces.com/contest/1511/problem/D)
I have an intutive approach but I want to know why he work??I want proof??
suppose we will use the first 5 character..
first: we will put the the characters at even position like that:
a_b_c_d_e_a_b_c_d_e_a_b_c_d_e

the the first k chars at even positions we will shift them by 1
and put  the shifted chars at odd positions like that
a_b_c_d_e
_b_c_d_e_a
abbccddeea

the second k chars at even positions we will shift them by 2
and put  the shifted chars at odd positions like that
a_b_c_d_e
_c_d_e_a_b
acbdcedaeb

you can say that the char at odd position j is equal to the char at position (j-1) plus number of shifts like s[j]=(s[j-1]+sh)%k;
sorry for my bad english...can someone prove it??


here's my submision

• -24

By mostafaabdelaal_03, history, 3 months ago,
hi..
how I can find the problems that based on grid and construct them, manipulate..
like these problems
1- G.(A/B Matrix)->https://codeforces.com/contest/1360/problem/G
2-D.(Grid-00100)->https://codeforces.com/problemset/problem/1371/D
I solved them and I got AC..but I want more and more ..I cannot find it in tags of codeforces..