|
|
package class23;
|
|
|
|
|
|
public class Code01_SplitSumClosed {
|
|
|
|
|
|
public static int right(int[] arr) {
|
|
|
if (arr == null || arr.length < 2) {
|
|
|
return 0;
|
|
|
}
|
|
|
int sum = 0;
|
|
|
for (int num : arr) {
|
|
|
sum += num;
|
|
|
}
|
|
|
return process(arr, 0, sum / 2);
|
|
|
}
|
|
|
|
|
|
// 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?
|
|
|
public static int process(int[] arr, int i, int rest) {
|
|
|
if (i == arr.length) {
|
|
|
return 0;
|
|
|
} else { // 还有数,arr[i]这个数
|
|
|
// 可能性1,不使用arr[i]
|
|
|
int p1 = process(arr, i + 1, rest);
|
|
|
// 可能性2,要使用arr[i]
|
|
|
int p2 = 0;
|
|
|
if (arr[i] <= rest) {
|
|
|
p2 = arr[i] + process(arr, i + 1, rest - arr[i]);
|
|
|
}
|
|
|
return Math.max(p1, p2);
|
|
|
}
|
|
|
}
|
|
|
|
|
|
public static int dp(int[] arr) {
|
|
|
if (arr == null || arr.length < 2) {
|
|
|
return 0;
|
|
|
}
|
|
|
int sum = 0;
|
|
|
for (int num : arr) {
|
|
|
sum += num;
|
|
|
}
|
|
|
sum /= 2;
|
|
|
int N = arr.length;
|
|
|
int[][] dp = new int[N + 1][sum + 1];
|
|
|
for (int i = N - 1; i >= 0; i--) {
|
|
|
for (int rest = 0; rest <= sum; rest++) {
|
|
|
// 可能性1,不使用arr[i]
|
|
|
int p1 = dp[i + 1][rest];
|
|
|
// 可能性2,要使用arr[i]
|
|
|
int p2 = 0;
|
|
|
if (arr[i] <= rest) {
|
|
|
p2 = arr[i] + dp[i + 1][rest - arr[i]];
|
|
|
}
|
|
|
dp[i][rest] = Math.max(p1, p2);
|
|
|
}
|
|
|
}
|
|
|
return dp[0][sum];
|
|
|
}
|
|
|
|
|
|
public static int[] randomArray(int len, int value) {
|
|
|
int[] arr = new int[len];
|
|
|
for (int i = 0; i < arr.length; i++) {
|
|
|
arr[i] = (int) (Math.random() * value);
|
|
|
}
|
|
|
return arr;
|
|
|
}
|
|
|
|
|
|
public static void printArray(int[] arr) {
|
|
|
for (int num : arr) {
|
|
|
System.out.print(num + " ");
|
|
|
}
|
|
|
System.out.println();
|
|
|
}
|
|
|
|
|
|
public static void main(String[] args) {
|
|
|
int maxLen = 20;
|
|
|
int maxValue = 50;
|
|
|
int testTime = 10000;
|
|
|
System.out.println("测试开始");
|
|
|
for (int i = 0; i < testTime; i++) {
|
|
|
int len = (int) (Math.random() * maxLen);
|
|
|
int[] arr = randomArray(len, maxValue);
|
|
|
int ans1 = right(arr);
|
|
|
int ans2 = dp(arr);
|
|
|
if (ans1 != ans2) {
|
|
|
printArray(arr);
|
|
|
System.out.println(ans1);
|
|
|
System.out.println(ans2);
|
|
|
System.out.println("Oops!");
|
|
|
break;
|
|
|
}
|
|
|
}
|
|
|
System.out.println("测试结束");
|
|
|
}
|
|
|
|
|
|
}
|