1177. Can Make Palindrome from Substring

Given a string s, we make queries on substrings of s.

For each query queries[i] = [left, right, k], we may rearrange the substring s[left], ..., s[right], and then choose up to k of them to replace with any lowercase English letter. 

If the substring is possible to be a palindrome string after the operations above, the result of the query is true. Otherwise, the result is false.

Return an array answer[], where answer[i] is the result of the i-th query queries[i].

Note that: Each letter is counted individually for replacement so if for example s[left..right] = "aaa", and k = 2, we can only replace two of the letters.  (Also, note that the initial string s is never modified by any query.)

 

Example :

Input: s = "abcda", queries = [[3,3,0],[1,2,0],[0,3,1],[0,3,2],[0,4,1]]
Output: [true,false,false,true,true]
Explanation:
queries[0] : substring = "d", is palidrome.
queries[1] : substring = "bc", is not palidrome.
queries[2] : substring = "abcd", is not palidrome after replacing only 1 character.
queries[3] : substring = "abcd", could be changed to "abba" which is palidrome. Also this can be changed to "baab" first rearrange it "bacd" then replace "cd" with "ab".
queries[4] : substring = "abcda", could be changed to "abcba" which is palidrome.

 

Constraints:

  • 1 <= s.length, queries.length <= 10^5
  • 0 <= queries[i][0] <= queries[i][1] < s.length
  • 0 <= queries[i][2] <= s.length
  • s only contains lowercase English letters.

Rust Solution

struct Solution;

impl Solution {
    fn can_make_pali_queries(s: String, queries: Vec<Vec<i32>>) -> Vec<bool> {
        let n = s.len();
        let mut prefix: Vec<u32> = vec![0; n + 1];
        for (i, c) in s.char_indices() {
            prefix[i + 1] = prefix[i] ^ (1 << (c as u32 - 'a' as u32));
        }
        let mut res = vec![];
        for q in queries {
            let left = q[0] as usize;
            let right = q[1] as usize + 1;
            let k = q[2] as u32;
            res.push(k * 2 >= (prefix[right] ^ prefix[left]).count_ones() - 1);
        }
        res
    }
}

#[test]
fn test() {
    let s = "abcda".to_string();
    let queries = vec_vec_i32![[3, 3, 0], [1, 2, 0], [0, 3, 1], [0, 3, 2], [0, 4, 1]];
    let res = vec![true, false, false, true, true];
    assert_eq!(Solution::can_make_pali_queries(s, queries), res);
}

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