uva_10604 - Chemical Reaction( Hash+状态压缩 )

这个题一开始想用六维数组直接跑的，但是考虑到药物或者序列更多的话就不实际了，这里我是用了hash对状态压缩然后DP
hash： elfhash
状态： 就是序列， 对应不同的结果保存最小解然后递归记忆求解

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

#define MAXV    10
#define MAXC    11
#define MAXN    1000001
#define INF     0x7fffffff

typedef struct NODE_ {
int heat;
char mix_rst;
}NODE;

int  hash[MAXN], ans;
NODE tab[MAXV][MAXV];
char save[MAXN][MAXC], t[MAXC];

inline int elf_hash(char *str)
{
unsigned long h( 0x0L ), x( 0x0L );
strcpy(t, str); char *ptr = t;
while( *ptr ) {
h = (h<<4)+(*ptr ++);
if( (x = h&0xF0000000L) ) {
h ^= (x>>24); h &= ~x;
}
}
int idx( h%MAXN );
while( (INF != hash[idx]) && strcmp(str, save[idx]) ) {
idx = (idx+1)%MAXN;
}
strcpy(save[idx], str); return idx;
}

inline int mix_chemical(const char *str, const int &idx1, const int &idx2, char *des)
{
int x, y, s, f, idx(0), flag(0);
x = str[idx1]-'0'; y = str[idx2]-'0';
s = min(idx1, idx2); f = max(idx1, idx2);
des[idx ++] = tab[x][y].mix_rst;
for(int i = 0; i < strlen(str); i ++) {
if( i != idx1 && i != idx2 ) {
des[idx ++] = str[i];
}
}
des[idx] = '\0'; return tab[x][y].heat;
}

int dfs(char *str)
{
if( 2 > strlen(str) ) {
return 0;
}
char tmp[MAXC];
int idx( elf_hash(str) ), rst(INF), x, y;
if( INF != hash[idx] ) {
return hash[idx];
}
for(int i = 0; i < strlen(str); i ++) {
for(int j = i+1; j < strlen(str); j ++) {
rst = min(rst, mix_chemical(str, i, j, tmp)+dfs(tmp));
rst = min(rst, mix_chemical(str, j, i, tmp)+dfs(tmp));
}
}
return hash[idx] = rst;
}

int main(int argc, char const *argv[])
{
#ifndef ONLINE_JUDGE
freopen("test.in", "r", stdin);
#endif
int cas, n, m, v;
char str[MAXC], ch[3];
scanf("%d", &cas);
for( ; cas; cas --) {
scanf("%d", &n);
for(int i = 1; i <= n; i ++) {
for(int j = 1; j <= n; j ++) {
scanf("%d %d", &v, &tab[i][j].heat);
tab[i][j].mix_rst = v+'0';
}
}
scanf("%d", &m);
for(int i = 0; i < m; i ++) {
scanf("%d", &v); str[i] = v+'0';
}
str[m] = '\0'; scanf("%s", ch); ans = INF;
memset(save, '\0', sizeof(save));
for(int i = 0; i < MAXN; i ++) {
hash[i] = INF;
}
printf("%d\n", dfs(str));
}
return 0;
}