Given a string, find the maximum consecutive repeating character in itself.

maxRepeatingChar

// given a string, give me the count of each particular character in the string.
// Hard mode: Give me the letter which is repeated the most in a row, regardless of how often the character appears in the string.
// “aaabbc”  would return “a”
// “aaabbbbc” would return “b”
// “aaabbbbaacc” would return “b”
// “abababababcccababababababab” would return “c”

let strArr = [
	`aaabbc`,  // a
	`aaabbbbc`, // b
	`aaabbbbaacc`, // b
	`abababababcccacacacacacacac`, // c
]

// complexity: 0(n^2) (two for loops)
//
const maxRepeatingChar_twoForLoops = (str) => {
	let len = str.length
	let max_count = 0

	// Find the maximum repeating character
	// starting from str[i]
	let res = str[0]
	for (let i = 0; i < len; i++) {
        // start with our first character
		let cur_count = 1
		for (let j = i + 1; j < len; j++) {
            // if our characrers don't match, break out
			if (str[i] != str[j]) {
                break
            }
            // matched - increase
			cur_count++
		}

		// Update result if required
		if (cur_count > max_count) {
			max_count = cur_count
			res = str[i]
		}
	}

    return res
}

const maxRepeatingChar_singleForLoop = (str) => {
	const n = str.length
	let max_count = 0
	let res = str[0]
	let cur_count = 1

	// Traverse string except last character
	for (let i = 0; i < n; i++) {
		// If current character matches with next
		if (i < n - 1 && str[i] == str[i + 1]) {
            cur_count++
		// If doesn't match, update result
		// (if required) and reset count
        } else {
			if (cur_count > count) {
				max_count = cur_count
				res = str[i]
			}
			cur_count = 1
		}
	}

	return res
}

// loop through test data
console.time(`two for loops`)
strArr.forEach((str) => {
	const res = maxRepeatingChar_twoForLoops(str)
    console.log(res)
})
console.timeEnd(`two for loops`);

console.time(`single for loop`)
strArr.forEach((str) => {
	const res = maxRepeatingChar_singleForLoop(str)
    console.log(res)
})
console.timeEnd(`single for loop`);