541. 反转字符串 II

void reversestring(char* s,int head,int tail){
    while(head<=tail){
        char temp=s[head];
        s[head]=s[tail];
        s[tail]=temp;
        head++;
        tail--;       
    }
}

char* reverseStr(char* s, int k) {
    int ns=0;
    while(s[ns]!=0) ns++;
    for(int i=0;i<ns;i+=2*k){
        if(ns-i>=2*k){
            reversestring(s,i,i+k-1);
        }else if(ns-i>=k){
            reversestring(s,i,i+k-1);
        }else{
            reversestring(s,i,ns-1);
        }
    }
    return s;   
}

结果：