【HDOJ】2546 饭卡

01背包，需要先对数据升序排序。这样保证优先购买最贵的东西，才满足背包条件。

 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>

 #define MAXNUM 1005

 int prices[MAXNUM];
 int dp[MAXNUM];

 int mymax(int a, int b) {
     return a>b ? a:b;
 }

 int comp(const void *a, const void *b) {
     return *(int *)b - *(int *)a;
 }

 int main() {
     int n, m;
     int i, j, tmp;

     while (scanf("%d", &n)!=EOF && n) {
         for (i=; i<=n; ++i) {
             scanf("%d", &prices[i]);
         }

         scanf("%d", &m);

         if (m < ) {
             printf("%d\n", m);
             continue;
         }

         qsort(prices+, n, sizeof(int), comp);
         memset(dp, , sizeof(dp));

         for (i=; i<=n; ++i) {
             for (j=m; j>=; --j) {
                 tmp = j - prices[i];
                 if (tmp >= ) {
                     dp[j] = mymax(dp[tmp]+prices[i], dp[j]);
                 } else {
                     dp[j] = mymax(prices[i], dp[j]);
                 }
             }
         }

         printf("%d\n", m-dp[m]);
     }

     return ;
 }