1894 - Find the Student that Will Replace the Chalk

JAVA

• class Solution {
      public int chalkReplacer(int[] chalk, int k) {
          int n = chalk.length;
          long[] prefixSums = new long[n];
          prefixSums[0] = chalk[0];
          for (int i = 1; i < n; i++)
              prefixSums[i] = prefixSums[i - 1] + chalk[i];
          long remainder = ((long) k) % prefixSums[n - 1];
          for (int i = 0; i < n; i++) {
              if (prefixSums[i] > remainder)
                  return i;
          }
          return -1;
      }
  }
  
  ############
  
  class Solution {
      public int chalkReplacer(int[] chalk, int k) {
          int n = chalk.length;
          long[] s = new long[n + 1];
          s[0] = chalk[0];
          for (int i = 1; i < n; ++i) {
              s[i] = s[i - 1] + chalk[i];
          }
          k %= s[n - 1];
          int left = 0, right = n - 1;
          while (left < right) {
              int mid = (left + right) >> 1;
              if (s[mid] > k) {
                  right = mid;
              } else {
                  left = mid + 1;
              }
          }
          return left;
      }
  }

C++

class Solution {
public:
    int chalkReplacer(vector<int>& A, int k) {
        long sum = accumulate(begin(A), end(A), 0L), i = 0, N  = A.size();
        k %= sum;
        while (k >= A[i]) {
            k -= A[i];
            ++i;
        }
        return i;
    }
};