【HDOJ】1114 Piggy-Bank

DP，先将coins按照重量排序可以优化。

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

#define MAXNUM  10005
#define COINNUM 505
#define MAXVAL  0x7fffffff
#define MYMIN(a, b) a<b ? a:b

typedef struct {
    int weight, val;
} coin_st;

coin_st coins[COINNUM];
int dp[MAXNUM];
int e, f;

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

int main() {
    int case_n, n;
    int i, j, left;

    scanf("%d", &case_n);
    dp[0] = 0;
    while (case_n--) {
        scanf("%d %d", &e, &f);
        scanf("%d", &n);
        for (i=0; i<n; ++i)
            scanf("%d %d", &coins[i].val, &coins[i].weight);
        qsort(coins, n, sizeof(coin_st), comp);

        for (i=1; i<=f-e; ++i) {
            dp[i] = MAXVAL;
            for (j=0; j<n; ++j) {
                left = i-coins[j].weight;
                if (left<0)
                    break;
                if (dp[left]!=MAXVAL && dp[left]+coins[j].val < dp[i])
                    dp[i] = dp[left]+coins[j].val;
            }
        }
        if (dp[f-e] == MAXVAL)
            printf("This is impossible.
");
        else
            printf("The minimum amount of money in the piggy-bank is %d.
", dp[f-e]);
    }

    return 0;
}