题解 | #双袋购物#

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);

        while(in.hasNext()){
            solution1(in);
            // solution2(in);
            // solution3(in);
        }
    }

    /**
     * 动态规划: 01背包(一维)[正+反]
     * 
     * dp[j]表示体积不超过j的最大价值
     * 
     * dpA[j] = Math.max(dpA[j], dpA[j-volumes[i]]+values[i])
     * 
     * dpB[j] = Math.max(dpB[j], dpB[j-volumes[i]]+values[i])
     * 
     * @param in
     */
    private static void solution1(Scanner in){
        int n = in.nextInt();
        int bagA = in.nextInt();
        int bagB = in.nextInt();

        int[] volumes = new int[n+1];
        int[] values = new int[n+1];
        for(int i=1; i<=n; i++){
            volumes[i] = in.nextInt();
            values[i] = in.nextInt();
        }

        int result = 0;

        // 正
        int[] dpA = new int[bagA+1];
        int[] ansA = new int[n+2];
        for(int i=1; i<n; i++){
            for(int j=bagA; j>=0; j--){
                // 选择装袋
                if(j >= volumes[i]){
                    dpA[j] = Math.max(dpA[j], dpA[j-volumes[i]]+values[i]);
                }
            }
            ansA[i] = dpA[bagA];
        }

        // 反
        int[] dpB = new int[bagB+1];
        int[] ansB = new int[n+2];
        for(int i=n; i>0; i--){
            for(int j=bagB; j>=0; j--){
                // 选择装袋
                if(j >= volumes[i]){
                    dpB[j] = Math.max(dpB[j], dpB[j-volumes[i]]+values[i]);
                }
            }
            ansB[i] = dpB[bagB];
        }

        // i点 换袋子
        for(int i=0; i<=n; i++){
            result = Math.max(result, ansA[i]+ansB[i+1]);
        }

        System.out.println(result);
    }

    /**
     * 动态规划: 01背包(二维)[正+反]
     *
     * dp[i][j]表示前i个物品体积不超过j的最大价值
     *
     * dpA[i][j] = dpA[i-1][j]
     * dpA[i][j] = Math.max(dpA[i][j], dpA[i-1][j-volumes[i]]+values[i])
     *
     * dpB[i][j] = dpB[i+1][j]
     * dpB[i][j] = Math.max(dpB[i][j], dpB[i+1][j-volumes[i]]+values[i])
     *
     * @param in
     */
    private static void solution2(Scanner in){
        int n = in.nextInt();
        int bagA = in.nextInt();
        int bagB = in.nextInt();

        int[] volumes = new int[n+1];
        int[] values = new int[n+1];
        for(int i=1; i<=n; i++){
            volumes[i] = in.nextInt();
            values[i] = in.nextInt();
        }

        int result = 0;

        // 正
        int[][] dpA = new int[n+2][bagA+1];
        for(int i=1; i<n; i++){
            for(int j=bagA; j>=0; j--){
                // 直接跳过
                dpA[i][j] = dpA[i-1][j];

                // 选择装袋
                if(j >= volumes[i]){
                    dpA[i][j] = Math.max(dpA[i][j], dpA[i-1][j-volumes[i]]+values[i]);
                }
            }
        }

        // 反
        int[][] dpB = new int[n+2][bagB+1];
        for(int i=n; i>0; i--){
            for(int j=bagB; j>=0; j--){
                // 直接跳过
                dpB[i][j] = dpB[i+1][j];

                // 选择装袋
                if(j >= volumes[i]){
                    dpB[i][j] = Math.max(dpB[i][j], dpB[i+1][j-volumes[i]]+values[i]);
                }
            }
        }

        // i点 换袋子
        for(int i=0; i<=n; i++){
            result = Math.max(result, dpA[i][bagA]+dpB[i+1][bagB]);
        }

        System.out.println(result);
    }

    /**
     * 动态规划: 01背包(二维) 超时!
     *
     * dp[i][j]表示前i个物品体积不超过j的最大价值
     *
     * dpA[i][j] = dpA[i-1][j]
     * dpA[i][j] = Math.max(dpA[i][j], dpA[i-1][j-volumes[i]]+values[i])
     *
     * dpB[i][j] = dpB[i-1][j]
     * dpB[i][j] = Math.max(dpB[i][j], dpB[i-1][j-volumes[i]]+values[i])
     *
     * @param in
     */
    private static void solution3(Scanner in){
        int n = in.nextInt();
        int bagA = in.nextInt();
        int bagB = in.nextInt();

        int[] volumes = new int[n+1];
        int[] values = new int[n+1];
        for(int i=1; i<=n; i++){
            volumes[i] = in.nextInt();
            values[i] = in.nextInt();
        }

        int result = 0;
        // 过point点后 换袋子
        for(int point=0; point<=n; point++){
            int[][] dpA = new int[n+1][bagA+1];
            int[][] dpB = new int[n+1][bagB+1];
            for(int i=1; i<=n; i++){
                if(i <= point){
                    for(int j=bagA; j>=0; j--){
                        // 直接跳过
                        dpA[i][j] = dpA[i-1][j];

                        // 选择装袋
                        if(j >= volumes[i]){
                            dpA[i][j] = Math.max(dpA[i][j], dpA[i-1][j-volumes[i]]+values[i]);
                        }
                    }
                }else{
                    for(int j=bagB; j>=0; j--){
                        // 直接跳过
                        dpB[i][j] = dpB[i-1][j];

                        // 选择装袋
                        if(j >= volumes[i]){
                            dpB[i][j] = Math.max(dpB[i][j], dpB[i-1][j-volumes[i]]+values[i]);
                        }
                    }
                }
            }
            result = Math.max(result, dpA[point][bagA]+dpB[n][bagB]);
        }

        System.out.println(result);
    }
}