README_EN.md

comments	difficulty	edit_url	rating	source	tags
true	Easy	https://github.com/doocs/leetcode/edit/main/solution/1700-1799/1758.Minimum%20Changes%20To%20Make%20Alternating%20Binary%20String/README_EN.md	1353	Weekly Contest 228 Q1	String

1758. Minimum Changes To Make Alternating Binary String

中文文档

Description

You are given a string s consisting only of the characters '0' and '1'. In one operation, you can change any '0' to '1' or vice versa.

The string is called alternating if no two adjacent characters are equal. For example, the string "010" is alternating, while the string "0100" is not.

Return the minimum number of operations needed to make s alternating.

 

Example 1:

Input: s = "0100"
Output: 1
Explanation: If you change the last character to '1', s will be "0101", which is alternating.

Example 2:

Input: s = "10"
Output: 0
Explanation: s is already alternating.

Example 3:

Input: s = "1111"
Output: 2
Explanation: You need two operations to reach "0101" or "1010".

 

Constraints:

• 1 <= s.length <= 104
• s[i] is either '0' or '1'.

Solutions

Solution 1

Python3

class Solution:
    def minOperations(self, s: str) -> int:
        cnt = sum(c != '01'[i & 1] for i, c in enumerate(s))
        return min(cnt, len(s) - cnt)

Java

class Solution {
    public int minOperations(String s) {
        int cnt = 0, n = s.length();
        for (int i = 0; i < n; ++i) {
            cnt += (s.charAt(i) != "01".charAt(i & 1) ? 1 : 0);
        }
        return Math.min(cnt, n - cnt);
    }
}

C++

class Solution {
public:
    int minOperations(string s) {
        int cnt = 0, n = s.size();
        for (int i = 0; i < n; ++i) cnt += s[i] != "01"[i & 1];
        return min(cnt, n - cnt);
    }
};

Go

func minOperations(s string) int {
	cnt := 0
	for i, c := range s {
		if c != []rune("01")[i&1] {
			cnt++
		}
	}
	return min(cnt, len(s)-cnt)
}

TypeScript

function minOperations(s: string): number {
    const n = s.length;
    let count = 0;
    for (let i = 0; i < n; i++) {
        count += s[i] !== '01'[i & 1] ? 1 : 0;
    }
    return Math.min(count, n - count);
}

Rust

impl Solution {
    pub fn min_operations(s: String) -> i32 {
        let n = s.len();
        let s = s.as_bytes();
        let cs = [b'0', b'1'];
        let mut count = 0;
        for i in 0..n {
            count += if s[i] != cs[i & 1] { 1 } else { 0 };
        }
        count.min(n - count) as i32
    }
}

C

#define min(a, b) (((a) < (b)) ? (a) : (b))

int minOperations(char* s) {
    int n = strlen(s);
    int count = 0;
    for (int i = 0; i < n; i++) {
        count += s[i] != ('0' + (i & 1)) ? 0 : 1;
    }
    return min(count, n - count);
}