数字统计2（数位dp=递归+记忆化搜索）

F2.cpp

@@ -0,0 +1,35 @@
+#include <cstdio>
+#include <cstring>
+
+#define rr register
+using namespace std;
+using ll=long long;
+ll dp[15][15], l, r;
+int dig[15];
+
+inline ll dfs(int dep, bool lim, bool ahe, int now, int sum) {
+    rr ll ans = 0;
+    if (!dep) return sum;
+    if (!lim && ahe && dp[dep][sum] != -1) return dp[dep][sum];
+    rr int mx = lim ? dig[dep] : 9;
+    for (rr int i = 0; i <= mx; ++i)
+        ans += dfs(dep - 1, lim && (i == mx), ahe || i, now, sum + ((ahe || i) && (i == now)));
+    if (!lim && ahe) dp[dep][sum] = ans;
+    return ans;
+}
+
+inline ll answ(ll x, int now) {
+    memset(dp, -1, sizeof(dp));
+    rr int len = 0;
+    while (x)
+        dig[++len] = x % 10, x /= 10;
+    return dfs(len, 1, 0, now, 0);
+}
+
+signed main() {
+    l = 1;
+    scanf("%d", &r);
+    for (rr int i = 0; i < 10; ++i)
+        printf("%lld%c", answ(r, i) - answ(l - 1, i), i == 9 ? 10 : 32);
+    return 0;
+}