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package class19;
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public class Code01_Knapsack {
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// 所有的货，重量和价值，都在w和v数组里
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// 为了方便，其中没有负数
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// bag背包容量，不能超过这个载重
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// 返回：不超重的情况下，能够得到的最大价值
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public static int maxValue(int[] w, int[] v, int bag) {
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if (w == null || v == null || w.length != v.length || w.length == 0) {
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return 0;
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}
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// 尝试函数！
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return process(w, v, 0, bag);
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}
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// index 0~N
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// rest 负~bag
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public static int process(int[] w, int[] v, int index, int rest) {
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if (rest < 0) {
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return -1;
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}
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if (index == w.length) {
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return 0;
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}
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int p1 = process(w, v, index + 1, rest);
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int p2 = 0;
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int next = process(w, v, index + 1, rest - w[index]);
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if (next != -1) {
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p2 = v[index] + next;
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}
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return Math.max(p1, p2);
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}
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public static int dp(int[] w, int[] v, int bag) {
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if (w == null || v == null || w.length != v.length || w.length == 0) {
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return 0;
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}
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int N = w.length;
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int[][] dp = new int[N + 1][bag + 1];
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for (int index = N - 1; index >= 0; index--) {
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for (int rest = 0; rest <= bag; rest++) {
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int p1 = dp[index + 1][rest];
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int p2 = 0;
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int next = rest - w[index] < 0 ? -1 : dp[index + 1][rest - w[index]];
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if (next != -1) {
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p2 = v[index] + next;
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}
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dp[index][rest] = Math.max(p1, p2);
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}
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}
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return dp[0][bag];
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}
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public static void main(String[] args) {
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int[] weights = { 3, 2, 4, 7, 3, 1, 7 };
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int[] values = { 5, 6, 3, 19, 12, 4, 2 };
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int bag = 15;
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System.out.println(maxValue(weights, values, bag));
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System.out.println(dp(weights, values, bag));
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}
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}
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