【DP】 ZOJ 2561 Order-Preserving Codes

#include <iostream>
#include <queue> 
#include <stack> 
#include <map> 
#include <set> 
#include <bitset> 
#include <cstdio> 
#include <algorithm> 
#include <cstring> 
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 2005
#define maxm 1000005
#define eps 1e-10
#define mod 1000000007
#define INF 1e17
#define PI (acos(-1.0))
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid 
#define rson o<<1 | 1, mid+1, R
#pragma comment(linker, "/STACK:16777216")
typedef long long LL;
typedef unsigned long long ULL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='
')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}
LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}
// head

LL dp[maxn][maxn];
int p[maxn], cnt;
int s[maxn][maxn];
LL sum[maxn];
int a[maxn];
int n;

void read(void)
{
	for(int i = 1; i <= n; i++) scanf("%d", &a[i]);
}

void dfs(int L, int R, int k)
{
	if(L == R) {
		for(int i = 0; i < cnt; i++) printf("%d", p[i]);
		printf("
");
		return;
	}
	p[cnt++] = 0;
	dfs(L, k, s[L][k]);
	p[cnt-1] = 1;
	dfs(k + 1, R, s[k+1][R]);
	cnt--;
}

void work(void)
{
	for(int i = 0; i <= n; i++)
		for(int j = 0; j <= n; j++)
			dp[i][j] = INF;
	for(int i = 1; i <= n; i++) sum[i] = sum[i-1] + a[i];
	for(int i = 1; i <= n; i++) dp[i][i] = sum[i] - sum[i-1], s[i][i] = i;
	for(int p = 1; p <= n; p++) {
		for(int i = 1; i + p <= n; i++) {
			int j = i + p;
			for(int k = s[i][j-1]; k <= s[i+1][j]; k++)
				if(dp[i][j] > dp[i][k] + dp[k+1][j] + sum[j] - sum[i-1]) {
					dp[i][j] = dp[i][k] + dp[k+1][j] + sum[j] - sum[i-1];
					s[i][j] = k;
				}
		}
	}
	dfs(1, n, s[1][n]);
}

int main(void)
{
	while(scanf("%d", &n) != EOF) {
		read();
		work();
	}

	return 0;
}