LeetCode-in-Java
1894. Find the Student that Will Replace the Chalk
Medium
There are n students in a class numbered from 0 to n - 1. The teacher will give each student a problem starting with the student number 0, then the student number 1, and so on until the teacher reaches the student number n - 1. After that, the teacher will restart the process, starting with the student number 0 again.
You are given a 0-indexed integer array chalk and an integer k. There are initially k pieces of chalk. When the student number i is given a problem to solve, they will use chalk[i] pieces of chalk to solve that problem. However, if the current number of chalk pieces is strictly less than chalk[i], then the student number i will be asked to replace the chalk.
Return the index of the student that will replace the chalk.
Example 1:
Input: chalk = [5,1,5], k = 22
Output: 0
Explanation: The students go in turns as follows:
-
Student number 0 uses 5 chalk, so k = 17.
-
Student number 1 uses 1 chalk, so k = 16.
-
Student number 2 uses 5 chalk, so k = 11.
-
Student number 0 uses 5 chalk, so k = 6.
-
Student number 1 uses 1 chalk, so k = 5.
-
Student number 2 uses 5 chalk, so k = 0.
Student number 0 does not have enough chalk, so they will have to replace it.
Example 2:
Input: chalk = [3,4,1,2], k = 25
Output: 1
Explanation: The students go in turns as follows:
-
Student number 0 uses 3 chalk so k = 22.
-
Student number 1 uses 4 chalk so k = 18.
-
Student number 2 uses 1 chalk so k = 17.
-
Student number 3 uses 2 chalk so k = 15.
-
Student number 0 uses 3 chalk so k = 12.
-
Student number 1 uses 4 chalk so k = 8.
-
Student number 2 uses 1 chalk so k = 7.
-
Student number 3 uses 2 chalk so k = 5.
-
Student number 0 uses 3 chalk so k = 2.
Student number 1 does not have enough chalk, so they will have to replace it.
Constraints:
chalk.length == n1 <= n <= 1051 <= chalk[i] <= 1051 <= k <= 109
Solution
public class Solution {
public int chalkReplacer(int[] chalk, int k) {
long localSum = sum(chalk);
int currentIndex = 0;
if (localSum != 0) {
int localK = (int) (k % localSum);
while (chalk[currentIndex] <= localK) {
localK -= chalk[currentIndex++];
}
}
return currentIndex;
}
private long sum(int[] chalk) {
long sum = 0;
for (int i : chalk) {
sum += i;
}
return sum;
}
}