2266. 统计打字方案数

2266. 统计打字方案数

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题目链接：2266. 统计打字方案数

代码如下：

class Solution {
public:
	int countTexts(string pressedKeys) {
		vector<long long> f(pressedKeys.size() + 1);
		f[0] = f[1] = 1;
		for (int i = 1; i < pressedKeys.size(); i++) {
			f[i + 1] = f[i];
			if (pressedKeys[i] == pressedKeys[i - 1]) {
				f[i + 1] += f[i - 1];
				if (i >= 2 && pressedKeys[i] == pressedKeys[i - 2]) {
					f[i + 1] += f[i - 2];
				}
				if (i >= 3 && (pressedKeys[i] == '7' || pressedKeys[i] == '9') && pressedKeys[i] == pressedKeys[i - 2] && pressedKeys[i] == pressedKeys[i - 3]) {
					f[i + 1] += f[i - 3];
				}
				f[i + 1] %= 1'000'000'007;
			}
		}
		return f[pressedKeys.size()];
	}
};