hdu 1074 Doing Homework 状态压缩的DP

#include <stdio.h>
#include <string.h>
#include <math.h>
#define MAX_DAY 200
#define MAX_STATUS 65536
#define MAX 0x7ffffff
char course[20][105];
int deadline[20], needtime[20];
int dp[MAX_STATUS], curday[MAX_STATUS], last[MAX_STATUS];
void pretreat(int maxstatus, int N) {
    int i, j, yw;
    memset(curday, 0, sizeof(int) * (maxstatus + 1));
    for (i = 0; i <= maxstatus; i++) {
        for (j = 0; j < N; j++) {
            yw = 1 << j;
            if (i & yw) {
                curday[i] += needtime[j];
            }
        }
    }
}
void printpath(int curstatus) {
    int temp, k;
    if(curstatus == 0) {
        return ;
    }
    printpath(last[curstatus]);
    temp = curstatus - last[curstatus];
    k = 0;
    while(temp > 1) {
        k++;
        temp >>= 1;
    }
    puts(course[k]);
}
int main() {
    int T, N;
    int i, j, maxstatus, temp, yw;
#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif
    scanf("%d", &T);
    while (T--) {
        scanf("%d", &N);
        maxstatus = 1 << N;
        maxstatus--;
        for (i = 0; i < N; i++) {
            scanf("%s %d %d", course[i], &deadline[i], &needtime[i]);
        }
        pretreat(maxstatus, N);
        dp[0] = 0;
        last[0] = 0;
        for (i = 1; i <= maxstatus; i++) {
            dp[i] = MAX;
            last[i] = MAX;
            for (j = 0; j < N; j++) {
                yw = 1 << j;
                if (yw & i) {
                    temp = curday[i] - deadline[j];
                    if (temp < 0) {
                        temp = 0;
                    }
                    temp += dp[i - yw];
                    if (dp[i] >= temp) {
                        dp[i] = temp;
                        if (last[i] > i - yw) {
                            last[i] = i - yw;
                        }
                    }
                }
            }
        }
        printf("%d\n", dp[maxstatus]);
        printpath(maxstatus);
    }
    return 0;
}
这题花了我好久才想明白，开始的时候用二维数组存储，超空间，后来才想到这种一维的方法。不过虽然已经AC了，我还是有一点没有明白，
就是输出路径的时候我只在每一种状态上记录了前一种状态，最后回溯输出，但我还不确定这样做是对的。路过的大牛帮我想想，指点一下我哈。