How hard is LeetCode 1247. Minimum Swaps to Make Strings Equal?

LeetCode 1247. Minimum Swaps to Make Strings Equal is rated Medium on LeetCode.

What is the time complexity of LeetCode 1247. Minimum Swaps to Make Strings Equal?

The Python solution on this page runs in O(n), where n is the length of the strings s_1 and s_2.

What is the space complexity of LeetCode 1247. Minimum Swaps to Make Strings Equal?

The Python solution on this page uses O(1) auxiliary space.

What topics does LeetCode 1247. Minimum Swaps to Make Strings Equal cover?

LeetCode 1247. Minimum Swaps to Make Strings Equal is tagged Greedy, Math and String on LeetCode.

Minimum Swaps to Make Strings Equal — LeetCode 1247 Python Solution

MediumGreedyMathString

Problem: #1247
Pattern: Greedy
Reading time: 2 min
Source: leetcode.com

The problem

You are given two strings s1 and s2 of equal length consisting of letters "x" and "y" only. Your task is to make these two strings equal to each other.

Example

Input: s1 = "xx", s2 = "yy"
Output: 1
Explanation: Swap s1[0] and s2[1], s1 = "yx", s2 = "yx".

Python solution

Python

class Solution:
    def minimumSwap(self, s1: str, s2: str) -> int:
        xy = yx = 0
        for a, b in zip(s1, s2):
            xy += a < b
            yx += a > b
        if (xy + yx) % 2:
            return -1
        return xy // 2 + yx // 2 + xy % 2 + yx % 2

Complexity

Measure	Complexity
Time	O(n), where n is the length of the strings s_1 and s_2
Space	O(1) auxiliary

Pattern: Greedy

Take the locally best option every time — when you can prove that never costs you later. LeetCode 1247. Minimum Swaps to Make Strings Equal is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Greedy.

The greedy guide has the Python template for the pattern and the 346 LeetCode problems that use it.

Frequently asked questions

How hard is LeetCode 1247. Minimum Swaps to Make Strings Equal?: LeetCode 1247. Minimum Swaps to Make Strings Equal is rated Medium on LeetCode.
What is the time complexity of LeetCode 1247. Minimum Swaps to Make Strings Equal?: The Python solution on this page runs in O(n), where n is the length of the strings s_1 and s_2.
What is the space complexity of LeetCode 1247. Minimum Swaps to Make Strings Equal?: The Python solution on this page uses O(1) auxiliary space.
What topics does LeetCode 1247. Minimum Swaps to Make Strings Equal cover?: LeetCode 1247. Minimum Swaps to Make Strings Equal is tagged Greedy, Math and String on LeetCode.