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821. Shortest Distance to a Character 👍

  • Time: $O(n)$
  • Space: $O(n)$
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class Solution {
 public:
  vector<int> shortestToChar(string s, char c) {
    const int n = s.length();
    vector<int> ans(n);
    int prev = -n;

    for (int i = 0; i < n; ++i) {
      if (s[i] == c)
        prev = i;
      ans[i] = i - prev;
    }

    for (int i = prev - 1; i >= 0; --i) {
      if (s[i] == c)
        prev = i;
      ans[i] = min(ans[i], prev - i);
    }

    return ans;
  }
};

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class Solution {
  public int[] shortestToChar(String s, char c) {
    final int n = s.length();
    int[] ans = new int[n];
    int prev = -n;

    for (int i = 0; i < n; ++i) {
      if (s[i] == c)
        prev = i;
      ans[i] = i - prev;
    }

    for (int i = prev - 1; i >= 0; --i) {
      if (s[i] == c)
        prev = i;
      ans[i] = Math.min(ans[i], prev - i);
    }

    return ans;
  }
}

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class Solution:
  def shortestToChar(self, s: str, c: str) -> List[int]:
    n = len(s)
    ans = [0] * n
    prev = -n

    for i in range(n):
      if s[i] == c:
        prev = i
      ans[i] = i - prev

    for i in range(prev - 1, -1, -1):
      if s[i] == c:
        prev = i
      ans[i] = min(ans[i], prev - i)

    return ans