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Copy pathLeetCode647.java
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69 lines (59 loc) · 2.06 KB
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package LeetCode.String;
import LeetCode.array.LeetCode64;
public class LeetCode647 {
private int count;
public int countSubstrings2(String s) {
if (s == null || s.length() == 0) return 0;
char[] arr = s.toCharArray();
for(int i = 0; i < s.length(); i++) {
expand(arr, i, i);
expand(arr, i, i+1);
}
return count;
}
private void expand(char[] arr, int l, int r) {
while(l >= 0 && r < arr.length && arr[l] == arr[r]){
count++;
l--;
r++;
}
}
// ===========================================
private char[] manacherStr(String s) {
char[] arr = s.toCharArray();
char[] manacherArr = new char[arr.length*2+1];
int index = 0;
for (int i = 0; i < manacherArr.length; i++) {
manacherArr[i] = (i & 1) == 0 ? '#' : arr[index++];
}
return manacherArr;
}
// 本想利用manacher算法来实现0（N）时间复杂度，但失败
public int countSubstrings(String s) {
if (s == null || s.length() == 0) return 0;
char[] arr = manacherStr(s);
int[] pArr = new int[arr.length];
int pr = 0, index=0, count = 0;
for (int i = 0; i < arr.length; i++) {
pArr[i] = i < pr ? Math.min(pArr[index*2-i], pr-i) : 1;
while (pArr[i]+i < arr.length && i-pArr[i] >= 0) {
if (arr[pArr[i]+i] == arr[i-pArr[i]]) {
pArr[i]++;
}else {
break;
}
}
if (pArr[i]+i > pr) {
pr = pArr[i] + i;
index = i;
}
// if ( ((i & 1) == 1 && pArr[i] > 2) || ((i & 1) == 0 && pArr[i] > 1)) count++;
}
return count + s.length();
}
public static void main(String[] args) {
LeetCode647 instance = new LeetCode647();
String s = "aaaaa";
System.out.println(instance.countSubstrings(s));
}
}