数位DP BZOJ 1026 [SCOI2009]windy数

#include <bits/stdc++.h>

int dp[10][10];
int digit[10];

int DFS(int pos, int val, int zero, bool limit) {
if (pos == -1) {
return 1;
}
int &now = dp[pos][val];
if (!limit && zero && now != -1) {
return now;
}
int d = limit ? digit[pos] : 9;
int ret = 0;
if (zero == 0) {
for (int i=0; i<=d; ++i) {
ret += DFS (pos - 1, i, i, limit && i == d);
}
} else {
for (int i=0; i<=d; ++i) {
if ((i-val) * (i - val) < 4) {
continue;
}
ret += DFS (pos - 1, i, 1, limit && i == d);
}
}
if (!limit && zero) {
now = ret;
}
return ret;
}

int solve(int x) {
int n = 0;
while (x) {
digit[n++] = x % 10;
x /= 10;
}
int ret = 0;
return DFS (n - 1, 0, 0, true);
}

int main() {
memset (dp, -1, sizeof (dp));
int a, b;
while (scanf ("%d%d", &a, &b) == 2) {
printf ("%d\n", solve (b) - solve (a - 1));
}
return 0;
}