UVA 624 01背包求方案

来源：互联网发布：朝鲜米格29知乎编辑：程序博客网时间：2024/06/06 00:38

题目：https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=565

题意：给定背包容量，给定物品个数，然后是物品，价值和体积相等。求最大价值时的放入方案，多解输出一解即可

思路：每次更新背包时顺便记录被谁跟新的即可，然后逆向求方案，正向输出

总结：背包和DP忘得差不多了。。。忧伤。。。是时候刷一波了

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int N = 10010;int dp[30][N], jl[30][N];int val[N], res[N];int main(){    int n, m;    while(~ scanf("%d", &n))    {        scanf("%d", &m);        for(int i = 0; i < m; i++)            scanf("%d", val + i);        memset(dp, 0, sizeof dp);        for(int i = 0; i < m; i++)            for(int j = 0; j <= n; j++)                if(j < val[i]) dp[i+1][j] = dp[i][j], jl[i+1][j] = -1;                else                {                    if(dp[i][j] < dp[i][j-val[i]] + val[i])                        dp[i+1][j] = dp[i][j-val[i]] + val[i], jl[i+1][j] = i; /*更新背包时记录由谁更新*/                    else dp[i+1][j] = dp[i][j], jl[i+1][j] = -1;                }                int tmp = n, k = 0;        for(int i = m; i >= 1; i--)            if(jl[i][tmp] != -1)                res[k++] = val[jl[i][tmp]], tmp = tmp - val[i-1];                for(int i = k - 1; i >= 0; i--)            printf("%d ", res[i]);        printf("sum:%d\n", dp[m][n]);    }    return 0;}

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