1247-MinimumSwapsToMakeStringsEqual.go

package main

// 1247. Minimum Swaps to Make Strings Equal
// 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. 
// You can swap any two characters that belong to different strings, which means: swap s1[i] and s2[j].

// Return the minimum number of swaps required to make s1 and s2 equal, or return -1 if it is impossible to do so.

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

// Example 2:
// Input: s1 = "xy", s2 = "yx"
// Output: 2
// Explanation: Swap s1[0] and s2[0], s1 = "yy", s2 = "xx".
// Swap s1[0] and s2[1], s1 = "xy", s2 = "xy".
// Note that you cannot swap s1[0] and s1[1] to make s1 equal to "yx", cause we can only swap chars in different strings.

// Example 3:
// Input: s1 = "xx", s2 = "xy"
// Output: -1

// Constraints:
//     1 <= s1.length, s2.length <= 1000
//     s1.length == s2.length
//     s1, s2 only contain 'x' or 'y'.

import "fmt"

func minimumSwap(s1 string, s2 string) int {
    xy, yx := 0, 0
    for i := range s1 {
        if s1[i] == 'x' && s2[i] == 'y' {
            xy++
        } else if s1[i] == 'y' && s2[i] == 'x' {
            yx++
        }
    }
    if (xy + yx) % 2 == 1 { // 没有方法能够使得这两个字符串相同，则返回 -1
        return -1 
    }
    return xy / 2 + yx / 2 + xy % 2 + yx % 2
}

func main() {
    // Example 1:
    // Input: s1 = "xx", s2 = "yy"
    // Output: 1
    // Explanation: Swap s1[0] and s2[1], s1 = "yx", s2 = "yx".
    fmt.Println(minimumSwap("xx", "yy")) // 1
    // Example 2:
    // Input: s1 = "xy", s2 = "yx"
    // Output: 2
    // Explanation: Swap s1[0] and s2[0], s1 = "yy", s2 = "xx".
    // Swap s1[0] and s2[1], s1 = "xy", s2 = "xy".
    // Note that you cannot swap s1[0] and s1[1] to make s1 equal to "yx", cause we can only swap chars in different strings.
    fmt.Println(minimumSwap("xy", "yx")) // 2
    // Example 3:
    // Input: s1 = "xx", s2 = "xy"
    // Output: -1
    fmt.Println(minimumSwap("xx", "xy")) // -1 

    fmt.Println(minimumSwap("xx", "yx")) // -1
}