Codeforces 164B || Codeforces 163A
Codeforces 164B
是个字符串问题(codeforces把这类问题归为two pointers),给了2个字符串a,b都可以任意移位,且b中无相等元素,满足条件“是a的子串==是b的子序列”的最大的串
Codeforces 163A
(x,y)其中x==y,x为字符串a的子串,y为字符串b的子序列,问这样的序偶有多少个?
解:这是个DP的问题
The problem could be solved with the following dynamic programming. Let f[i, j] be the number of distinct pairs (“substring starting at position i” and “subsequence of the substring t[j… |t|]”)
Then:
f[i, j] = f[i, j + 1];
if (s[i] == t[j])
add(f[i, j], f[i + 1, j + 1] + 1)
Answer = f[i,0]