[leetcode] Reverse Words in a String

最新推荐文章于 2024-01-04 11:20:32 发布

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本文介绍了一道LeetCode经典题目“翻转字符串中的单词”的两种解法。第一种解法利用栈来存储单词，然后依次弹出实现翻转；第二种解法采用双指针从字符串末尾开始寻找单词并进行翻转。这两种方法均能有效地解决该问题。

From : https://leetcode.com/problems/reverse-words-in-a-string/

Given an input string, reverse the string word by word.

For example,
Given s = "the sky is blue",
return "blue is sky the".


class Solution {
public:
    void reverseWords(string &s) {
        stack<string> stc;
		string tstr="";
		s += ' ';
		int len = s.length();
		for(int i=0; i<len; i++) {
			if(i==0 && s[i]==' ') continue;
			if(s[i]==' ' && s[i-1]==' ') continue;
			if(s[i]==' ' && tstr!="") {
				stc.push(tstr);
				tstr = "";
			} else {
				tstr += s[i];
			}
		}
		s="";
		while(!stc.empty()) {
			s += stc.top();
			stc.pop();
			if(stc.empty()) {
				break;
			}
			s += " ";
		}
    }
};

Solution 2：

class Solution {
public:
    void reverseWords(string &s) {
        string ts;
		int end = s.size()-1, start = end;
		while(end>=0) {
			while(end>=0 && s[end]==' ') end--;
			start = end;
			while(start>=0 && s[start]!=' ') start--;
			if(start!=0 && start<end && ts!="") ts.append(" ");
			if(start < end) ts.append(s.substr(start+1, end-start));			
			end = start;
		}
		s = ts;
    }
};