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package class24;
import java.util.HashMap;
import java.util.HashSet;
public class Code01_Split4Parts {
public static boolean canSplits1(int[] arr) {
if (arr == null || arr.length < 7) {
return false;
}
HashSet<String> set = new HashSet<String>();
int sum = 0;
for (int i = 0; i < arr.length; i++) {
sum += arr[i];
}
int leftSum = arr[0];
for (int i = 1; i < arr.length - 1; i++) {
set.add(String.valueOf(leftSum) + "_" + String.valueOf(sum - leftSum - arr[i]));
leftSum += arr[i];
}
int l = 1;
int lsum = arr[0];
int r = arr.length - 2;
int rsum = arr[arr.length - 1];
while (l < r - 3) {
if (lsum == rsum) {
String lkey = String.valueOf(lsum * 2 + arr[l]);
String rkey = String.valueOf(rsum * 2 + arr[r]);
if (set.contains(lkey + "_" + rkey)) {
return true;
}
lsum += arr[l++];
} else if (lsum < rsum) {
lsum += arr[l++];
} else {
rsum += arr[r--];
}
}
return false;
}
public static boolean canSplits2(int[] arr) {
if (arr == null || arr.length < 7) {
return false;
}
// key 某一个累加和, value出现的位置
HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
int sum = arr[0];
for (int i = 1; i < arr.length; i++) {
map.put(sum, i);
sum += arr[i];
}
int lsum = arr[0]; // 第一刀左侧的累加和
for (int s1 = 1; s1 < arr.length - 5; s1++) { // s1是第一刀的位置
int checkSum = lsum * 2 + arr[s1]; // 100 x 100 100*2 + x
if (map.containsKey(checkSum)) {
int s2 = map.get(checkSum); // j -> y
checkSum += lsum + arr[s2];
if (map.containsKey(checkSum)) { // 100 * 3 + x + y
int s3 = map.get(checkSum); // k -> z
if (checkSum + arr[s3] + lsum == sum) {
return true;
}
}
}
lsum += arr[s1];
}
return false;
}
public static int[] generateRondomArray() {
int[] res = new int[(int) (Math.random() * 10) + 7];
for (int i = 0; i < res.length; i++) {
res[i] = (int) (Math.random() * 10) + 1;
}
return res;
}
public static void main(String[] args) {
int testTime = 3000000;
for (int i = 0; i < testTime; i++) {
int[] arr = generateRondomArray();
if (canSplits1(arr) ^ canSplits2(arr)) {
System.out.println("Error");
}
}
}
}