859. Buddy Strings
Given two strings A and B of lowercase letters, return true if you can swap two letters in A so the result is equal to B, otherwise, return false.
Swapping letters is defined as taking two indices i and j (0-indexed) such that i != j and swapping the characters at A[i] and A[j]. For example, swapping at indices 0 and 2 in "abcd" results in "cbad".
Example 1:
Input: A = "ab", B = "ba" Output: true Explanation: You can swap A[0] = 'a' and A[1] = 'b' to get "ba", which is equal to B.
Example 2:
Input: A = "ab", B = "ab" Output: false Explanation: The only letters you can swap are A[0] = 'a' and A[1] = 'b', which results in "ba" != B.
Example 3:
Input: A = "aa", B = "aa" Output: true Explanation: You can swap A[0] = 'a' and A[1] = 'a' to get "aa", which is equal to B.
Example 4:
Input: A = "aaaaaaabc", B = "aaaaaaacb" Output: true
Example 5:
Input: A = "", B = "aa" Output: false
Constraints:
0 <= A.length <= 200000 <= B.length <= 20000AandBconsist of lowercase letters.
Rust Solution
struct Solution;
use std::collections::HashSet;
impl Solution {
fn buddy_strings(a: String, b: String) -> bool {
let a: Vec<char> = a.chars().collect();
let b: Vec<char> = b.chars().collect();
let n = a.len();
let m = b.len();
if n != m {
return false;
}
if a == b {
let mut hs: HashSet<char> = HashSet::new();
let mut sum = 0;
for &c in &a {
if !hs.insert(c) {
sum += 1;
}
}
sum != 0
} else {
let mut pair: Vec<usize> = vec![];
for i in 0..n {
if a[i] != b[i] {
pair.push(i);
}
}
if pair.len() == 2 {
let i = pair[0];
let j = pair[1];
a[i] == b[j] && a[j] == b[i]
} else {
false
}
}
}
}
#[test]
fn test() {
let a = "ab".to_string();
let b = "ba".to_string();
assert_eq!(Solution::buddy_strings(a, b), true);
let a = "ab".to_string();
let b = "ab".to_string();
assert_eq!(Solution::buddy_strings(a, b), false);
let a = "aa".to_string();
let b = "aa".to_string();
assert_eq!(Solution::buddy_strings(a, b), true);
let a = "aaaaaaabc".to_string();
let b = "aaaaaaacb".to_string();
assert_eq!(Solution::buddy_strings(a, b), true);
let a = "".to_string();
let b = "aa".to_string();
assert_eq!(Solution::buddy_strings(a, b), false);
}
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