1758. Minimum Changes To Make Alternating Binary String

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# 題目敘述

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".5)

# 解題思路

# Solution

class Solution {

    public int minOperations(String s) {

        int len = s.length();

        int diff = 0;

        for (int i = 0; i < len; i++) {

            if (i % 2 == 0 && s.charAt(i) != '1') {

                diff++;

            }else if (i % 2 == 1 && s.charAt(i) != '0') {

                diff++;

            }

        }

        return Math.min(diff, len - diff);

    }

}