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// @Title: 统计道路上的碰撞次数 (Count Collisions on a Road)
// @Author: 15816537946@163.com
// @Date: 2022-03-20 13:07:47
// @Runtime: 48 ms
// @Memory: 16 MB
class Solution {
public:
    int countCollisions(string directions) {
        int ans = 0;
        bool flag = false;
        for (char c : directions) {
            if (c == 'R' || c == 'S') flag = true;
            else if (flag) ans++;
        }
        flag = false;
        for (int i = (int) directions.size() - 1; i >= 0; i--) {
            char c = directions[i];
            if (c == 'L' || c == 'S') flag = true;
            else if (flag) ans++;
        }
        return ans;
    }
};