new file: P2657.cpp

2026-08-26 20:54:31 +08:00
parent 942a77955d
commit c9255ff7b9
1 changed files with 89 additions and 0 deletions
@@ -0,0 +1,89 @@
+#include <bits/stdc++.h>
+using namespace std;
+int a, b;
+int dp[15][15];
+int getlen(int num)
+{
+    if (num < 10)
+        return 1;
+    int cnt = 0;
+    while (num)
+    {
+        num /= 10;
+        cnt++;
+    }
+    return cnt;
+}
+int calc(int x)
+{
+    if (x <= 0)
+        return 0;
+    vector<int> digit;
+    while (x)
+    {
+        digit.push_back(x % 10);
+        x /= 10;
+    }
+    int len = digit.size();
+    int res = 0;
+    for (int i = 1; i < len; ++i)
+    {
+        for (int j = 1; j <= 9; ++j)
+        {
+            res += dp[i][j];
+        }
+    }
+    for (int i = len - 1; i >= 0; --i)
+    {
+        int cur = digit[i];
+        int start = (i == len - 1) ? 1 : 0;
+        for (int j = start; j < cur; ++j)
+        {
+            if (i == len - 1 || abs(j - digit[i + 1]) >= 2)
+            {
+                if (i == 0)
+                {
+                    ++res;
+                }
+                else
+                {
+                    res += dp[i + 1][j];
+                }
+            }
+        }
+        if (i != len - 1 && abs(cur - digit[i + 1]) < 2)
+        {
+            break;
+        }
+        if (i == 0)
+        {
+            ++res;
+        }
+    }
+    return res;
+}
+
+int main()
+{
+    scanf("%d%d", &a, &b);
+    int _b = getlen(b);
+    for (int i = 0; i <= 9; ++i)
+    {
+        dp[1][i] = 1;
+    }
+    for (int i = 2; i <= _b; ++i)
+    {
+        for (int j = 0; j <= 9; ++j)
+        {
+            for (int k = 0; k <= 9; ++k)
+            {
+                if (abs(j - k) < 2)
+                    continue;
+                dp[i][j] += dp[i - 1][k];
+            }
+        }
+    }
+
+    printf("%d\n", calc(b) - calc(a - 1));
+    return 0;
+}