BZOJ1222 [HNOI2001]产品加工 - 动态规划- 背包

题解

怎么看都不像是个背包，直到我看了题解→_→， 第一次碰到这么奇怪的背包= =

定一个滚动数组$F_i$， $i$表示机器$a$用了$i$的时间， $F_i$表示机器$b$用了$F_i$的时间， 然后就直接可以进行滚动转移了。。。

真是开眼界啊QuQ

代码

 #include<cstring>
 #include<algorithm>
 #include<cstdio>
 #define rd read()
 #define rep(i,a,b) for(register int i = (a); i <= (b); ++i)
 #define per(i,a,b) for(register int i = (a); i >= (b); --i)
 using namespace std;

 const int N = 8e3, inf = ~0U >> ;

 int n, m, f[N << ];
 int a[N], b[N], ab[N];

 inline int read() {
     int X = , p = ; char c = getchar();
     for(; c > '' || c < ''; c = getchar()) if(c == '-') p = -;
     for(; c >= '' && c <= ''; c = getchar()) X = X *  + c - '';
     return X * p;
 }

 inline int cmax(int A, int B) {
     return A > B ? A : B;
 }

 inline int cmin(int A, int B) {
     return A > B ? B : A;
 }

 int main()
 {
     n = rd;
     rep(i, , n) {
         a[i] = rd;
         b[i] = rd;
         ab[i] = rd;
         m += cmax(a[i], ab[i]);
     }
     f[] = ;
     rep(i, , n) per(j, m, ) {
         int tmp = inf;
         if(a[i] && j - a[i] >= ) tmp = cmin(tmp, f[j - a[i]]);
         if(ab[i] && j - ab[i] >= ) tmp = cmin(tmp, f[j - ab[i]] + ab[i]);
         if(b[i]) tmp = cmin(tmp, f[j] + b[i]);
         f[j] = tmp;
     }
     int ans = inf;
     rep(i ,, m) ans = cmin(ans, cmax(i, f[i]));
     printf("%d\n", ans);
 }