LightOJ 1140 How Many Zeroes?(数位DP)

#include <cstdio>
#include <cstring>

typedef long long lld;

lld dp[15][11][15][2], n, m;
int bit[15];

lld dfs(int len, int x, int sum, int s, int fp){
if (len == 0){
return (lld)(sum + s);
}
if (!fp && dp[len][x][sum][s] != -1)return dp[len][x][sum][s];
int Max = (fp ? bit[len] : 9);
lld ret = 0;
for (int i = 0; i <= Max; i++){
ret += dfs(len-1, i, sum + (!s && i == 0), s && i == 0, fp && i == Max);
}
if (!fp) dp[len][x][sum][s] = ret;
return ret;
}

lld solve(lld x){
if (x < 0)return 0;
else if (x == 0)return 1;
int len = 0;
while (x){
bit[++len] = x % 10;
x /= 10;
}
return dfs(len, bit[len], 0, 1, 1);
}

int main(){
int T;
scanf("%d", &T);
memset(dp, -1, sizeof(dp));
for (int cas = 1; cas <= T; cas++){
scanf("%lld%lld", &n, &m);
printf("Case %d: %lld\n", cas, solve(m) - solve(n-1));
}
return 0;
}