Count Collisions on a Road LeetCode solution in Java

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/*
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cars on left side which are moving in left direction are never going to collide,
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Similarly, cars on right side which are moving right side are never going to collide.
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In between them every car is going to collide.
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*/
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class Solution {
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  public int countCollisions(String directions) {
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    int left = 0, right = directions.length() - 1;
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    while (left < directions.length() && directions.charAt(left) == 'L') {
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      left++;
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    }
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    while (right >= 0 && directions.charAt(right) == 'R') {
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      right--;
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    }
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    int count = 0;
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    for (int i = left; i <= right; i++) {
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      if (directions.charAt(i) != 'S') {
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        count++;
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      }
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    }
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    // combining these three loops - TC : O(N).
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    return count;
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  }
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}