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package class23;
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public class Code01_SplitSumClosed {
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public static int right(int[] arr) {
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if (arr == null || arr.length < 2) {
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return 0;
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}
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int sum = 0;
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for (int num : arr) {
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sum += num;
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}
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return process(arr, 0, sum / 2);
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}
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// arr[i...]可以自由选择，请返回累加和尽量接近rest，但不能超过rest的情况下，最接近的累加和是多少？
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public static int process(int[] arr, int i, int rest) {
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if (i == arr.length) {
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return 0;
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} else { // 还有数，arr[i]这个数
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// 可能性1，不使用arr[i]
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int p1 = process(arr, i + 1, rest);
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// 可能性2，要使用arr[i]
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int p2 = 0;
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if (arr[i] <= rest) {
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p2 = arr[i] + process(arr, i + 1, rest - arr[i]);
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}
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return Math.max(p1, p2);
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}
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}
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public static int dp(int[] arr) {
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if (arr == null || arr.length < 2) {
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return 0;
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}
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int sum = 0;
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for (int num : arr) {
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sum += num;
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}
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sum /= 2;
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int N = arr.length;
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int[][] dp = new int[N + 1][sum + 1];
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for (int i = N - 1; i >= 0; i--) {
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for (int rest = 0; rest <= sum; rest++) {
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// 可能性1，不使用arr[i]
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int p1 = dp[i + 1][rest];
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// 可能性2，要使用arr[i]
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int p2 = 0;
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if (arr[i] <= rest) {
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p2 = arr[i] + dp[i + 1][rest - arr[i]];
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}
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dp[i][rest] = Math.max(p1, p2);
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}
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}
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return dp[0][sum];
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}
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public static int[] randomArray(int len, int value) {
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int[] arr = new int[len];
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for (int i = 0; i < arr.length; i++) {
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arr[i] = (int) (Math.random() * value);
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}
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return arr;
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}
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public static void printArray(int[] arr) {
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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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}
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public static void main(String[] args) {
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int maxLen = 20;
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int maxValue = 50;
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int testTime = 10000;
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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 len = (int) (Math.random() * maxLen);
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int[] arr = randomArray(len, maxValue);
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int ans1 = right(arr);
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int ans2 = dp(arr);
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if (ans1 != ans2) {
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printArray(arr);
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System.out.println(ans1);
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System.out.println(ans2);
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System.out.println("Oops!");
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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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