HDU 3555 Bomb(数位DP)

ACM

题目地址：HDU 3555

题意： 
问(0, n]里面有几个数有'49'这个子串。

分析： 
裸数位DP。 
直接用DFS做。 
就是输入输出比较坑，杭电貌似都要用__int64。

代码：

/**  Author:      illuz <iilluzen[at]gmail.com>*  File:        3555.cpp*  Create Date: 2014-07-26 16:04:07*  Descripton:  digit dp */#include <cstdio>#include <cstring>#include <iostream>#include <cmath>using namespace std;#define RI(x) scanf("%d",&x)#define PIN(x) printf("%d\n",x)typedef long long ll;const int N = 30;ll z[N] = {1};int t;int bit[N];ll dp[N][2], n;ll dfs(int len, bool is4, bool ismax) {if (len == 0)return 0;if (!ismax && dp[len][is4] >= 0)return dp[len][is4];ll cnt = 0;  int mmax = ismax ? bit[len] : 9;for (int i = 0; i <= mmax; i++) {if (is4 && i == 9) {cnt += ismax ? n % z[len-1] + 1 : z[len-1];} else {cnt += dfs(len - 1, i == 4, ismax && bit[len] == i);}}return ismax ? cnt : dp[len][is4] = cnt;}ll solve(ll n) {int len = 0;while (n) {bit[++len] = n % 10;n /= 10;}bit[len + 1] = 0;return dfs(len, false, true);}int main() {memset(dp, -1, sizeof(dp));for (int i = 1; i < N; i++) {z[i] = z[i - 1] * 10;}RI(t);while (t--) {scanf("%I64d", &n);printf("I64d\n", solve(n));//cin >> n;//cout << solve(n) << endl;}return 0;}