231130 광고 삽입

public String solution(String playTime, String advTime, String[] logs) {
	int playTimeSeconds = timeToInt(playTime);
	int advTimeSeconds = timeToInt(advTime);

	int[] accumulatedTime = new int[playTimeSeconds+1];

	for (String log : logs) {
		String[] l = log.split("-");
		int start = timeToInt(l[0]);
		int end = timeToInt(l[1]);
		for (int i = start; i < end; i++) {
			accumulatedTime[i]++;
		}
	}

	int optimalStartTime = findOptimalStartTime(accumulatedTime, advTimeSeconds);

	return timeToString(optimalStartTime);
}

private int timeToInt(String time) {
	String[] times = time.split(":");
	int toSec = 3600;
	int totalTime = 0;

	for (String t : times) {
		int num = Integer.parseInt(t);
		totalTime += num * toSec;
		toSec /= 60;
	}

	return totalTime;
}

private String timeToString(int time) {
	int hour = time / 3600;
	int minute = (time % 3600) / 60;
	int second = time % 60;

	return String.format("%02d:%02d:%02d", hour, minute, second);
}

private int findOptimalStartTime(int[] accumulatedTime, int advTimeSeconds) {
	long maxSum = 0;
	long sum = 0;
	int optimalStartTime = 0;

	for (int i = 0; i < advTimeSeconds; i++) {
		sum += accumulatedTime[i];
	}
	maxSum = sum;

	for (int i = advTimeSeconds; i < accumulatedTime.length; i++) {
		sum += accumulatedTime[i] - accumulatedTime[i - advTimeSeconds];

		if (sum > maxSum) {
			maxSum = sum;
			optimalStartTime = i - advTimeSeconds + 1;
		}
	}

	return optimalStartTime;
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/72414