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// 不要拷贝包信息的内容
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package class39;
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// 课堂版本
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// 本文件是Code02_SnacksWays问题的牛客题目解答
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// 但是用的分治的方法
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// 这是牛客的测试链接：
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// https://www.nowcoder.com/questionTerminal/d94bb2fa461d42bcb4c0f2b94f5d4281
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// 请同学们务必参考如下代码中关于输入、输出的处理
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// 这是输入输出处理效率很高的写法
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// 提交如下的代码，并把主类名改成"Main"
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// 可以直接通过
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import java.util.Map.Entry;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.io.OutputStreamWriter;
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import java.io.PrintWriter;
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import java.io.StreamTokenizer;
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import java.util.TreeMap;
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public class Code02_SnacksWaysMain1 {
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public static void main(String[] args) throws IOException {
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BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
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StreamTokenizer in = new StreamTokenizer(br);
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PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
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while (in.nextToken() != StreamTokenizer.TT_EOF) {
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int n = (int) in.nval;
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in.nextToken();
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int bag = (int) in.nval;
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int[] arr = new int[n];
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for (int i = 0; i < n; i++) {
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in.nextToken();
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arr[i] = (int) in.nval;
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}
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long ways = ways(arr, bag);
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out.println(ways);
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out.flush();
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}
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}
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public static long ways(int[] arr, int bag) {
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if (arr == null || arr.length == 0) {
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return 0;
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}
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if (arr.length == 1) {
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return arr[0] <= bag ? 2 : 1;
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}
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int mid = (arr.length - 1) >> 1;
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TreeMap<Long, Long> lmap = new TreeMap<>();
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long ways = process(arr, 0, 0, mid, bag, lmap);
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TreeMap<Long, Long> rmap = new TreeMap<>();
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ways += process(arr, mid + 1, 0, arr.length - 1, bag, rmap);
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TreeMap<Long, Long> rpre = new TreeMap<>();
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long pre = 0;
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for (Entry<Long, Long> entry : rmap.entrySet()) {
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pre += entry.getValue();
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rpre.put(entry.getKey(), pre);
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}
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for (Entry<Long, Long> entry : lmap.entrySet()) {
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long lweight = entry.getKey();
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long lways = entry.getValue();
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Long floor = rpre.floorKey(bag - lweight);
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if (floor != null) {
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long rways = rpre.get(floor);
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ways += lways * rways;
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}
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}
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return ways + 1;
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}
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// arr 30
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// func(arr, 0, 14, 0, bag, map)
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// func(arr, 15, 29, 0, bag, map)
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// 从index出发，到end结束
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// 之前的选择，已经形成的累加和sum
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// 零食[index....end]自由选择，出来的所有累加和，不能超过bag，每一种累加和对应的方法数，填在map里
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// 最后不能什么货都没选
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// [3,3,3,3] bag = 6
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// 0 1 2 3
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// - - - - 0 -> （0 : 1）
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// - - - $ 3 -> （0 : 1）(3, 1)
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// - - $ - 3 -> （0 : 1）(3, 2)
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public static long func(int[] arr, int index, int end, long sum, long bag, TreeMap<Long, Long> map) {
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if (sum > bag) {
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return 0;
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}
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// sum <= bag
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if (index > end) { // 所有商品自由选择完了！
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// sum
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if (sum != 0) {
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if (!map.containsKey(sum)) {
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map.put(sum, 1L);
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} else {
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map.put(sum, map.get(sum) + 1);
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}
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return 1;
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} else {
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return 0;
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}
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}
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// sum <= bag 并且 index <= end(还有货)
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// 1) 不要当前index位置的货
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long ways = func(arr, index + 1, end, sum, bag, map);
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// 2) 要当前index位置的货
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ways += func(arr, index + 1, end, sum + arr[index], bag, map);
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return ways;
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}
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public static long process(int[] arr, int index, long w, int end, int bag, TreeMap<Long, Long> map) {
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if (w > bag) {
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return 0;
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}
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if (index > end) {
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if (w != 0) {
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if (!map.containsKey(w)) {
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map.put(w, 1L);
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} else {
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map.put(w, map.get(w) + 1);
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}
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return 1;
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} else {
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return 0;
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}
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} else {
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long ways = process(arr, index + 1, w, end, bag, map);
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ways += process(arr, index + 1, w + arr[index], end, bag, map);
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return ways;
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}
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}
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} |
