1208. Get Equal Substrings Within Budget

You are given two strings `s` and `t` of the same length. You want to change `s` to `t`. Changing the `i`-th character of `s` to `i`-th character of `t` costs `|s[i] - t[i]|` that is, the absolute difference between the ASCII values of the characters.

You are also given an integer `maxCost`.

Return the maximum length of a substring of `s` that can be changed to be the same as the corresponding substring of `t`with a cost less than or equal to `maxCost`.

If there is no substring from `s` that can be changed to its corresponding substring from `t`, return `0`.

Example 1:

```Input: s = "abcd", t = "bcdf", maxCost = 3
Output: 3
Explanation: "abc" of s can change to "bcd". That costs 3, so the maximum length is 3.```

Example 2:

```Input: s = "abcd", t = "cdef", maxCost = 3
Output: 1
Explanation: Each character in s costs 2 to change to charactor in `t, so the maximum length is 1.`
```

Example 3:

```Input: s = "abcd", t = "acde", maxCost = 0
Output: 1
Explanation: You can't make any change, so the maximum length is 1.
```

Constraints:

• `1 <= s.length, t.length <= 10^5`
• `0 <= maxCost <= 10^6`
• `s` and `t` only contain lower case English letters.

1208. Get Equal Substrings Within Budget
``````struct Solution;

impl Solution {
fn equal_substring(s: String, t: String, max_cost: i32) -> i32 {
let s: Vec<char> = s.chars().collect();
let t: Vec<char> = t.chars().collect();
let n = s.len();
let mut cost: Vec<i32> = vec![0; n];
for i in 0..n {
cost[i] = (s[i] as i32 - t[i] as i32).abs();
}
let mut start = 0;
let mut end = 0;
let mut res = 0;
let mut sum = 0;
while end < n {
if sum <= max_cost {
sum += cost[end];
end += 1;
} else {
sum -= cost[start];
start += 1;
}
if sum <= max_cost {
res = res.max(end - start);
}
}
res as i32
}
}

#[test]
fn test() {
let s = "abcd".to_string();
let t = "cdef".to_string();
let max_cost = 3;
let res = 1;
assert_eq!(Solution::equal_substring(s, t, max_cost), res);
let s = "abcd".to_string();
let t = "acde".to_string();
let max_cost = 0;
let res = 1;
assert_eq!(Solution::equal_substring(s, t, max_cost), res);
}
``````