英文:
Using Priority Queue with Custom Comparator to Sort Based on Number of Words in a String?
问题
Comparator<String> whiteSpaces = new Comparator<String>() {
@Override
public int compare(String s1, String s2) {
int count1 = 0;
int count2 = 0;
char c = ' ';
for (int i = 0; i < s1.length(); i++) {
if (s1.charAt(i) == c) {
count1++;
}
}
for (int i = 0; i < s2.length(); i++) {
if (s2.charAt(i) == c) {
count2++;
}
}
return count1 - count2;
}
};
英文:
I'm trying to use Priority Queue to sort strings based on how many words (white spaces) there are in each string. My code works only in certain scenerios, but not when the amount of white spaces per string is really spread out. I think because my methods aren't comparing them all.
Comparator<String> whiteSpaces = new Comparator<String>() {
int count1 = 0;
int count2 = 0;
char c = ' ';
@Override
public int compare(String s1, String s2) {
for(int i = 0; i < s1.length(); i++) {
if(s1.charAt(i) == c){
count1++;
}
}
for(int i = 0; i < s2.length(); i++) {
if(s2.charAt(i) == c) {
count2++;
}
}
return count1 - count2;
}
};
Could I modify what I have so that it compares to all the strings added to the priorityqueue? Thanks in advance.
答案1
得分: 1
Comparator无法正常工作，因为您在调用compare()之间没有将count1和count2重置为0。
实际上，问题在于count1和count2是字段。它们应该是局部变量。
将count1和count2的声明移到方法内部。
Comparator<String> whiteSpaces = new Comparator<String>() {
char c = ' ';
@Override
public int compare(String s1, String s2) {
int count1 = 0;
int count2 = 0;
for(int i = 0; i < s1.length(); i++) {
if(s1.charAt(i) == c){
count1++;
}
}
for(int i = 0; i < s2.length(); i++) {
if(s2.charAt(i) == c) {
count2++;
}
}
return count1 - count2;
}
};
其他改进：
-
字段
c应该是private和final的，并且命名更合适。 -
创建一个辅助方法以消除重复的代码。
-
使用
Integer.compare(a, b)来替代减法。
Comparator<String> whiteSpaces = new Comparator<String>() {
private final char separator = ' ';
@Override
public int compare(String s1, String s2) {
return Integer.compare(countSeparators(s1), countSeparators(s2));
}
private int countSeparators(String s) {
int count = 0;
for (int i = 0; i < s.length(); i++) {
if (s.charAt(i) == separator) {
count++;
}
}
return count;
}
};
英文:
The Comparator isn't working because you don't reset count1 and count2 to 0 between calls to compare().
Actually, the problem is that count1 and count2 are fields. They should be local variables.
Move count1 and count2 declarations into the method.
Comparator<String> whiteSpaces = new Comparator<String>() {
char c = ' ';
@Override
public int compare(String s1, String s2) {
int count1 = 0;
int count2 = 0;
for(int i = 0; i < s1.length(); i++) {
if(s1.charAt(i) == c){
count1++;
}
}
for(int i = 0; i < s2.length(); i++) {
if(s2.charAt(i) == c) {
count2++;
}
}
return count1 - count2;
}
};
Other improvements:
-
Field
cshould beprivateandfinal, and better named. -
Create a helper method to eliminate repeated code.
-
Use
Integer.compare(a, b)instead of subtraction.
<!-- -->
Comparator<String> whiteSpaces = new Comparator<String>() {
private final char separator = ' ';
@Override
public int compare(String s1, String s2) {
return Integer.compare(countSeparators(s1), countSeparators(s2));
}
private int countSeparators(String s) {
int count = 0;
for (int i = 0; i < s.length(); i++) {
if (s.charAt(i) == separator) {
count++;
}
}
return count;
}
};
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