HDU2089 不要62 BZOJ1026: [SCOI2009]windy数 [数位DP]

基础题复习
这次用了dfs写法，感觉比较好

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
const int N=10;
inline int read(){
	char c=getchar();int x=0,f=1;
	while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}
	while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}
	return x*f;
}

int r, l, a[N], len;
int f[N][2];
int dfs(int d, bool flag, bool sky) { //printf("dfs %d %d %d
",d,flag,sky);
	if(d==0) return 1;
	if(!sky && f[d][flag]!=-1) return f[d][flag];
	int now=0, lim = sky ? a[d] : 9;
	for(int i=0; i<=lim; i++) {
		if(i==4 || (flag && i==2)) continue;
		now += dfs(d-1, i==6, i==lim && sky);
	}
	return sky ? now : f[d][flag]=now;
}
int cal(int n) {
	len=0;
	while(n) a[++len]=n%10, n/=10;
	return dfs(len, 0, 1);
}
int main() {
	freopen("in","r",stdin);
	memset(f, -1, sizeof(f));
	while(true) {
		l=read(); r=read();
		if(l==0 && r==0) break;
		printf("%d
", cal(r)-cal(l-1));
	}
}

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
const int N=15;
inline int read(){
	char c=getchar();int x=0,f=1;
	while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}
	while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}
	return x*f;
}

int l, r, a[N], len;
int f[N][N];
int dfs(int d, int last, bool zero, bool sky) { //printf("Dfs %d %d  %d
",d,last,sky);
	if(d==0) return 1;
	if(!sky && !zero && f[d][last]!=-1) return f[d][last];
	int now=0, lim = sky ? a[d] : 9; //printf("lim %d
",lim);
	for(int i=0; i<=lim; i++) 
		if(zero || abs(i-last)>=2) now += dfs(d-1, i, zero && i==0, sky && i==lim);
	return (sky||zero) ? now : f[d][last]=now;
}
int cal(int n) {
	len=0;
	while(n) a[++len]=n%10, n/=10;
	return dfs(len, 0, 1, 1);
}
int main() {
	freopen("in","r",stdin);
	memset(f,-1,sizeof(f));
	//for(int i=0; i<=50; i+=10) printf("hi %d  %d 
",i,cal(i));
	//printf("hi %d %d
",24,cal(24));
	l=read(); r=read();
	printf("%d
", cal(r)-cal(l-1));
}