例如，"student. a am I"，正確的句子應該是 "I am a student."
解題思路
先使用空格將字串切割為字串陣列，再重新拼接新的字串
public class Solution {
public String ReverseSentence(String str) {
if(str == null || str.trim().length() == 0) {
return str;
}
String[] strs = str.split(" ");
StringBuilder sb = new StringBuilder();
for(int i = strs.length - 1; i >= 0; i--) {
sb.append(strs[i]);
if(i != 0) {
sb.append(" ");
}
}
return sb.toString();
}
}
第二種思路，先翻轉整個句子，然后，依次翻轉每個單詞，依據空格來確定單詞的起始和終止位置
public class Solution {
public String ReverseSentence(String str) {
if(str == null || str.trim().length() == 0) {
return str;
}
char[] chars = str.toCharArray();
reverse(chars, 0, chars.length - 1);
int blank = -1;
for(int i = 0; i < chars.length; i++) {
if(chars[i] == ' ') {
int nextBlank = i;
reverse(chars, blank + 1, nextBlank - 1);
blank = nextBlank;
}
}
// 對最后一個單詞單獨進行反轉
reverse(chars, blank + 1, chars.length - 1);
return new String(chars);
}
public void reverse(char[] chars, int low, int high){
while(low < high){
char temp = chars[low];
chars[low] = chars[high];
chars[high] = temp;
low++;
high--;
}
}
}
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