Problems

1. string tokeniser
2. sort strings based on column

String Tokeniser

Design a string tokeniser function

View the code

#include<bits/stdc++.h>
using namespace std;

char * token(char *arr, char del){
static char *curr=NULL;
if(arr!=NULL){
    curr=arr;
}

if(curr==NULL) return NULL;

char *out = new char[strlen(curr)+1];
int i;
for(i=0;curr[i]!='\0';i++){
    if(curr[i]!=del){
    out[i]=curr[i];
    } else{
        out[i]='\0';
        curr+=i+1;
        return out;
    }
}
out[i]='\0';
curr=NULL;
return out;
}

int main(){
    char s[100]="This is a string";
    char *ptr = token(s,' ');
    cout<<(ptr)<<endl;

    while(ptr!=NULL){
        ptr = token(NULL,' ');
        cout<<ptr<<endl;
    }
}

sort strings based on column

Sort the strings based on following constraints:

• key: short the string based on some key(column number)
• ordering: order the string either by numeric comparision or lexicographical comparision
• reversal: reverse the array if provided as true else keep it in same order

View the code

#include<bits/stdc++.h>
using namespace std;

string getColumn(string s, int key){
    char *ans=strtok((char*)s.c_str()," ");
    while(key>1){
    ans=strtok(NULL," ");
    key--;
    }
    return (string)ans;
}

int stringToInt(string a){
    int n = a.length();
    int ans=0;
    int i=0,p=1;
    while(i<n){
        ans*=p;
        ans+=(a[i]-'0');
        i++;
        p*=10;
    }
    return ans;
}

bool compareNumeric(pair<string,string> a, pair<string,string> b){
int key1=stringToInt(a.second);
int key2=stringToInt(b.second);
return (key1<key2);
}

bool compareLexicographically(pair<string,string> a, pair<string,string> b){
return (a.second<b.second);
}

int main(){
    int n;cin>>n;
    cin.get();
    string a[n];
    for(int i=0;i<n;i++){
        getline(cin,a[i]);
    }
    int key;
    string reversal, ordering;
    cin>>key>>reversal>>ordering;
    pair <string,string> b[100];
    for(int i=0;i<n;i++){
        b[i].first = a[i];
        b[i].second = getColumn(a[i], key);
    }
    if(ordering=="numeric"){
        sort(b,b+n, compareNumeric);
    }else{
        sort(b,b+n, compareLexicographically);
    }

    if(reversal=="false"){
        for(int i=0;i<n;i++) cout<<b[i].first<<endl;
    }else{
        for(int i=n-1;i>=0;i--) cout<<b[i].first<<endl;
    }
}