秋叶集

class Solution {
public:
    int minimumOperations(string leaves) {
        int n = leaves.size();
        vector<vector<int>> f(n, vector<int>(3));
        f[0][0] = (leaves[0] == 'y');
        f[0][1] = f[0][2] = f[1][2] = INT_MAX;
        for (int i = 1; i < n; ++i) {
            int isRed = (leaves[i] == 'r');
            int isYellow = (leaves[i] == 'y');
            f[i][0] = f[i - 1][0] + isYellow;
            f[i][1] = min(f[i - 1][0], f[i - 1][1]) + isRed;
            if (i >= 2) {
                f[i][2] = min(f[i - 1][1], f[i - 1][2]) + isYellow;
            }
        }
        return f[n - 1][2];
    }
};

看懂了 简单