# DP on Strings

Given two strings s1 and s2, return some result.

Most of the problems on this pattern requires a solution that can be accepted in O(n^2) complexity.

```java
// i - indexing string s1
// j - indexing string s2
for (int i = 1; i <= n; ++i) {
   for (int j = 1; j <= m; ++j) {
       if (s1[i-1] == s2[j-1]) {
           dp[i][j] = /*code*/;
       } else {
           dp[i][j] = /*code*/;
       }
   }
}
```

> If you are given one string `s` the approach may little vary

```java
for (int l = 1; l < n; ++l) {
   for (int i = 0; i < n-l; ++i) {
       int j = i + l;
       if (s[i] == s[j]) {
           dp[i][j] = /*code*/;
       } else {
           dp[i][j] = /*code*/;
       }
   }
}
```

