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package class_2022_04_2_week;
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// 来自美团
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// 3.26笔试
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// 给定一个非负数组，任意选择数字，使累加和最大且为7的倍数，返回最大累加和
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// n比较大，10的5次方
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public class Code03_MaxSumDividedBy7 {
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public static int maxSum1(int[] arr) {
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return process1(arr, 0, 0);
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}
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public static int process1(int[] arr, int index, int pre) {
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if (index == arr.length) {
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return pre % 7 == 0 ? pre : 0;
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}
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int p1 = process1(arr, index + 1, pre);
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int p2 = process1(arr, index + 1, pre + arr[index]);
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return Math.max(p1, p2);
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}
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public static int maxSum2(int[] arr) {
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if (arr == null || arr.length == 0) {
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return 0;
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}
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int n = arr.length;
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int[][] dp = new int[n][7];
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for (int i = 0; i < n; i++) {
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for (int j = 1; j < 7; j++) {
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dp[i][j] = -1;
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}
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}
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dp[0][arr[0] % 7] = arr[0];
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for (int i = 1; i < n; i++) {
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// 当前arr[i] % 7 的余数
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int curMod = arr[i] % 7;
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for (int j = 0; j < 7; j++) {
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dp[i][j] = dp[i - 1][j];
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int findMod = (7 - curMod + j) % 7;
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if (dp[i - 1][findMod] != -1) {
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dp[i][j] = Math.max(dp[i][j], dp[i - 1][findMod] + arr[i]);
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}
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}
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}
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return dp[n - 1][0] == -1 ? 0 : dp[n - 1][0];
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}
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// 为了测试
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public static int[] randomArray(int n, int v) {
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int[] arr = new int[n];
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for (int i = 0; i < n; i++) {
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arr[i] = (int) (Math.random() * v) + 1;
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}
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return arr;
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}
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// 为了测试
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public static void main(String[] args) {
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int len = 12;
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int value = 30;
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int testTime = 2000;
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System.out.println("测试开始");
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for (int i = 0; i < testTime; i++) {
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int n = (int) (Math.random() * len) + 1;
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int[] arr = randomArray(n, value);
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int ans1 = maxSum1(arr);
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int ans2 = maxSum2(arr);
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if (ans1 != ans2) {
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System.out.println("出错了!");
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for (int num : arr) {
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System.out.print(num + " ");
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}
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System.out.println();
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System.out.println(ans1);
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System.out.println(ans2);
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break;
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}
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}
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System.out.println("测试结束");
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}
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}
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