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 alterna

minOperations.js

/**
 * @param {string} s
 * @return {number}
 */
var minOperations = function(s) {
    // cost0 = number of flips needed if we force pattern "010101..."
    // cost1 = number of flips needed if we force pattern "101010..."
    let cost0 = 0;
    let cost1 = 0;

    for (let i = 0; i < s.length; i++) {
        // For pattern starting with '0':
        // even index → '0', odd index → '1'
        const expected0 = (i % 2 === 0) ? '0' : '1';

        // For pattern starting with '1':
        // even index → '1', odd index → '0'
        const expected1 = (i % 2 === 0) ? '1' : '0';

        // Count mismatches for each pattern
        if (s[i] !== expected0) cost0++;
        if (s[i] !== expected1) cost1++;
    }

    // The minimum flips needed to match either valid alternating pattern
    return Math.min(cost0, cost1);
};