P1282-多米诺骨牌

 1 #include <bits/stdc++.h>
 2 #define maxn 13003
 3 #define _for(i,a,b) for(int i = (a);i < b;i ++)
 4 typedef long long ll;
 5 using namespace std;
 6 inline ll read()
 7 {
 8     ll ans = 0;
 9     char ch = getchar(), last = ' ';
10     while(!isdigit(ch)) last = ch, ch = getchar();
11     while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
12     if(last == '-') ans = -ans;
13     return ans;
14 }
15 inline void write(ll x)
16 {
17     if(x < 0) x = -x, putchar('-');
18     if(x >= 10) write(x / 10);
19     putchar(x % 10 + '0');
20 }
21 int N,V = 0;
22 int base = 0;
23 int m[maxn];
24 int d[maxn];
25 int dp[maxn];
26 int vs[maxn];
27 
28 int main()
29 {
30     memset(dp,0,sizeof(dp));
31     memset(m,0,sizeof(m));
32     N = read();
33     _for(i,0,N)
34     {
35         int a = read(),b = read();
36         if(a<b)
37             m[i] = -1,base++;
38         else if(a>b)
39             m[i] = 1;
40         int t = abs(a-b);
41         V += t;
42         d[i] = t*2;
43     }
44     
45     vs[0] = 1;
46     _for(i,0,N)
47     for(int v = V+6000; v >= 0; v --)
48         if(vs[v-d[i]])
49             if(!vs[v])
50                 dp[v] = dp[v-d[i]]+m[i],vs[v] = 1;
51             else
52                 dp[v] = min(dp[v],dp[v-d[i]]+m[i]);
53 
54     int vv = V;
55     int d = 0;
56     while(!vs[vv])
57     {
58         vv += d;
59         if(!d || d>0)
60             d ++;
61         d *= -1;
62     }
63     
64     write(base+min(dp[V+d],dp[V-d]));
65     printf("\n");
66     return 0;
67 }