春节7天练 | Day 4：散列表和字符串

Reverse String

void reverseString(char* s, int sSize) {
    int left = 0,right = sSize-1;
     char tmp;
    while(left<right)
    { 
        tmp = s[left];
        s[left] = s[right];
        s[right] = tmp;
        left+=1;
        right-=1;
    }
    return s;
}

Reverse Words in a String

void trimMoreSpaces(char *s)
{
    int cur=0,need=0;
    bool first = false;
    while(s[cur])
    {
        if(s[cur]!=' ')
        {
            s[need++] = s[cur++];
            first = true;
        }
        else
        {
            if(first)
            {
                s[need++]=s[cur++];
                first = false;
            }
            else cur++;
        }
    }
     if (need >= 1 && s[need - 1] == ' ') s[need - 1] = 0;
    else s[need] = 0;
}
void reverse(char *s,int left,int right)
{
    char tmp;
    while(left<right)
    {
        tmp = s[left];
        s[left] = s[right];
        s[right] = tmp;
        left++;right--;
    }
}
void reverseWords(char *s) {
   if(!s||!s[0])
       return;
   trimMoreSpaces(s);
   if(!s[0])
        return;
   int end= 0;
   while (s[end++]); 
   end -= 2; 
   reverse(s,0,end);
   /**
    i love you
    uoy evol i
   */
   int pos = 0,i=1;
    while(true)
    {
        if(s[i]&&s[i]!=' ')i++;
        else if(s[i]==' '||!s[i])
        {
            int left = pos,right=i-1;
            reverse(s,left,right);
            if(!s[i]) return;
            i++;pos=i++;
        }
    }
}

string to integer atoi

int myAtoi(char* s) {
    if(!s)
        return 0;
    bool first = true;
    int len = strlen(s);
    int i = 0,sign=1;
    while(s[i++]==' '&&i<len);
    i-=1;
     if(s[i]=='-')
    {
        sign = -1;
        i++;
    }
    else if (s[i] == '+')
    {
        sign = 1;
        i++;
    }
    first = s[i]>='0'&&s[i]<='9';
    if(!first)
        return 0;
    long long pow = 10,result;
    len = 1;
    first = true;
    while(s[i]>='0'&&s[i]<='9')
    {
        if(first)
        {
            if(s[i]=='0')
            {
                i++;
                continue;
            }
            else
            {
                first = false;
                i++;
            }
        }else
        {
            len++;
            i++;
        }
    }
    i-=1;
    //return i;
    for(int j=0;j<len;j++)
    {
        if(j==0)
        {
            result = s[i] - '0';
            i--;
        }
            
        else
        {
            if(pow>INT_MAX||result>INT_MAX)
            {
                if(sign==1)
                    return INT_MAX;
                else
                    return INT_MIN;
            }
            result+=(s[i]-'0')*pow;
            pow*=10;
            i--;
        }
    }
    //return result;
    if(result-1>=INT_MAX&&sign==-1)
        return INT_MIN;
    else if(result-1<(INT_MAX))
    {
        //return result;
        if(sign == -1)
            return sign*result;
        else if(result==INT_MAX)
            return INT_MAX;
        else
            return result;
    }else
        return INT_MAX;
}