剑指offer 字符串专题 刷题记录（2）

import java.util.*;
public class Solution {
    public String ReverseSentence(String str) {
        if(str.trim().equals("")){
            return str;
        }
        String[] s=str.split(" ");
        StringBuffer sb=new StringBuffer();
        for(int i=s.length-1;i>=0;i--){
            sb.append(s[i]);
            if(i!=0){
                  sb.append(" ");
            }
        }
        return sb.toString();
    }
}

public class Solution {
    public String ReverseSentence(String str) {
        char[] chars=str.toCharArray();
        reverse(chars,0,str.length()-1);
        int blank=-1;
        for(int i=0;i<str.length();i++){
            if(chars[i]==' '){
                int nextblank=i;
                reverse(chars,blank+1,nextblank-1);
                blank=nextblank;
            }
        }
        reverse(chars,blank+1,str.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--;
        }
    }
}

public class Solution {
    public int StrToInt(String str) {
        if(str==null||str.trim().equals("")){
            return 0;
        }
        int symbol=1;
        int start=0;
        char[] chars=str.trim().toCharArray();
        if(chars[0]=='+'){
            start=1;
        }else if(chars[0]=='-'){
            symbol=-1;
            start=1;
        }
        int result=0;
        for(int i=start;i<chars.length;i++){
            if(chars[i]>'9'||chars[i]<'0'){
                return 0;
            }
            result=result*10+(int)(chars[i]-'0');
            if((symbol==1&&result>Integer.MAX_VALUE)||(symbol==-1&&-result<Integer.MIN_VALUE)){
                return 0;
            }
        }
        return symbol*result;
    }
}