P2657 [SCOI2009] windy 数

https://www.luogu.com.cn/record/85898393

Luogu/P2657/P2657.cpp

@@ -0,0 +1,74 @@
+#include <iostream>
+#include <cmath>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 15;
+
+int a, b, f[N][N];
+
+std::vector<int> gen(int x) {
+    std::vector<int> res;
+
+    while (x) {
+        res.push_back(x % 10);
+        x /= 10;
+    }
+
+    return res;
+}
+
+int calc(int x) {
+    int res = 0;
+    auto num = gen(x);
+
+    for (int i = 1; i < num.size(); i++) {
+        for (int j = 1; j < 10; j++) {
+            res += f[i][j];
+        }
+    }
+
+    for (int i = 1; i < *num.rbegin(); i++) {
+        res += f[num.size()][i];
+    }
+
+    for (int i = num.size() - 1; i; i--) {
+        for (int j = 0; j < num[i - 1]; j++) {
+            if (std::abs(j - num[i]) >= 2) {
+                res += f[i][j];
+            }
+        }
+
+        if (std::abs(num[i] - num[i - 1]) < 2) break;
+    }
+
+    return res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> a >> b;
+
+    for (int i = 0; i < 10; i++) {
+        f[1][i] = 1;
+    }
+
+    for (int i = 2; i <= 10; i++) {
+        for (int j = 0; j < 10; j++) {
+            for (int k = 0; k < 10; k++) {
+                if (std::abs(j - k) >= 2) {
+                    f[i][j] += f[i - 1][k];
+                }
+            }
+        }
+    }
+
+    cout << calc(b + 1) - calc(a) << endl;
+
+    return 0;
+}