README_EN.md

1790. Check if One String Swap Can Make Strings Equal

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Description

You are given two strings s1 and s2 of equal length. A string swap is an operation where you choose two indices in a string (not necessarily different) and swap the characters at these indices.

Return true if it is possible to make both strings equal by performing at most one string swap on exactly one of the strings. Otherwise, return false.

 

Example 1:

Input: s1 = "bank", s2 = "kanb"
Output: true
Explanation: For example, swap the first character with the last character of s2 to make "bank".

Example 2:

Input: s1 = "attack", s2 = "defend"
Output: false
Explanation: It is impossible to make them equal with one string swap.

Example 3:

Input: s1 = "kelb", s2 = "kelb"
Output: true
Explanation: The two strings are already equal, so no string swap operation is required.

 

Constraints:

• 1 <= s1.length, s2.length <= 100
• s1.length == s2.length
• s1 and s2 consist of only lowercase English letters.

Solutions

Python3

class Solution:
    def areAlmostEqual(self, s1: str, s2: str) -> bool:
        cnt = 0
        c1 = c2 = None
        for a, b in zip(s1, s2):
            if a != b:
                cnt += 1
                if cnt > 2 or (cnt == 2 and (a != c2 or b != c1)):
                    return False
                c1, c2 = a, b
        return cnt != 1

Java

class Solution {
    public boolean areAlmostEqual(String s1, String s2) {
        int cnt = 0;
        char c1 = 0, c2 = 0;
        for (int i = 0; i < s1.length(); ++i) {
            char a = s1.charAt(i), b = s2.charAt(i);
            if (a != b) {
                if (++cnt > 2 || (cnt == 2 && (a != c2 || b != c1))) {
                    return false;
                }
                c1 = a;
                c2 = b;
            }
        }
        return cnt != 1;
    }
}

C++

class Solution {
public:
    bool areAlmostEqual(string s1, string s2) {
        int cnt = 0;
        char c1 = 0, c2 = 0;
        for (int i = 0; i < s1.size(); ++i) {
            char a = s1[i], b = s2[i];
            if (a != b) {
                if (++cnt > 2 || (cnt == 2 && (a != c2 || b != c1))) {
                    return false;
                }
                c1 = a, c2 = b;
            }
        }
        return cnt != 1;
    }
};

Go

func areAlmostEqual(s1 string, s2 string) bool {
	cnt := 0
	var c1, c2 byte
	for i := range s1 {
		a, b := s1[i], s2[i]
		if a != b {
			cnt++
			if cnt > 2 || (cnt == 2 && (a != c2 || b != c1)) {
				return false
			}
			c1, c2 = a, b
		}
	}
	return cnt != 1
}

C

bool areAlmostEqual(char *s1, char *s2) {
    int n = strlen(s1);
    int i1 = -1;
    int i2 = -1;
    for (int i = 0; i < n; i++) {
        if (s1[i] != s2[i]) {
            if (i1 == -1) {
                i1 = i;
            } else if (i2 == -1) {
                i2 = i;
            } else {
                return 0;
            }
        }
    }
    if (i1 == -1 && i2 == -1) {
        return 1;
    }
    if (i1 == -1 || i2 == -1) {
        return 0;
    }
    return s1[i1] == s2[i2] && s1[i2] == s2[i1];
}

TypeScript

function areAlmostEqual(s1: string, s2: string): boolean {
    let c1, c2;
    let cnt = 0;
    for (let i = 0; i < s1.length; ++i) {
        const a = s1.charAt(i);
        const b = s2.charAt(i);
        if (a != b) {
            if (++cnt > 2 || (cnt == 2 && (a != c2 || b != c1))) {
                return false;
            }
            c1 = a;
            c2 = b;
        }
    }
    return cnt != 1;
}

Rust

impl Solution {
    pub fn are_almost_equal(s1: String, s2: String) -> bool {
        if s1 == s2 {
            return true;
        }
        let (s1, s2) = (s1.as_bytes(), s2.as_bytes());
        let mut idxs = vec![];
        for i in 0..s1.len() {
            if s1[i] != s2[i] {
                idxs.push(i);
            }
        }
        if idxs.len() != 2 {
            return false;
        }
        s1[idxs[0]] == s2[idxs[1]] && s2[idxs[0]] == s1[idxs[1]]
    }
}

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