Vijos - P1071 新年趣事之打牌

思路

先用背包求出能否凑成left，还要一边记录路径。

然后递归打印路径即可。

二维数组开不下，滚一下就行。

代码

#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define MP(a, b) make_pair(a, b)
const int MAXN = 100000 + 10;
const int INF = 0x3f3f3f3f;

int dp[MAXN], card[110], path[MAXN];
bool first = true;

void PrintAns(int num)
{
    if (path[num] == -1)
        return;
    int x = path[num];
    PrintAns(num - card[x]);
    if (first)
        printf("%d", x), first = false;
    else
        printf(" %d", x);
}

int main()
{
    //freopen("input.txt", "r", stdin);
    int w, n, i, j, left, sum = 0;
    scanf("%d%d", &w, &n);
    for (i = 1; i <= n; i++)
    {
        scanf("%d", &card[i]);
        sum += card[i];
    }
    left = sum - w;
    dp[0] = 1;
    path[0] = -1;
    for (i = 1; i <= n; i++)
        for (j = sum; j >= card[i]; j--)
        {
            if (!dp[j] && dp[j - card[i]] > 0)    //这个状态还没达到并且将要达到
                path[j] = i;
            dp[j] += dp[j - card[i]];
        }
    if (dp[left] > 1)
    {
        printf("-1\n");
        return 0;
    }
    if (!dp[left])
    {
        printf("0\n");
        return 0;
    }
    PrintAns(left);
    puts("");
    return 0;
}