错误：C++ 中的“]”标记之前的预期主表达式

Question

I'm trying to create something similar to string.find with vectors c++98 , but I can't fix this error. I have simplified the code and left only the error. If I can get help on how to achieve this.

#include <iostream>
#define MAX 99999
using namespace std;

int free_pos (int v[]);
int find_line (int v[], int pos);

int main() {
   char text[MAX];
   int loc_key[MAX],start_line[MAX]; //

   for(int i=0; i<free_pos(loc_key);i++) {
       cout << "Line: " << i+1;
       int pos = find_line(start_line[],loc_key[i]); //Here is the error
       for(int j=start_line[pos];j<start_line[pos+1];j++) {
            cout<<text[j];
       }
       cout<<endl;
   }
   return 0;
}

int free_pos (int v[]) {
    for(int i=0;i<MAX;i++){
        if(v[i] == 0)
            return i;
    }
    return 99;
}

int find_line (int v[], int pos) {
    for(int i=0; i<free_pos(v); i++) {
        if(v[i]==pos)
            return v[i];
        if(v[i]< pos)
            return v[i-1];
    }
}

Answer 1

Your both functions

int free_pos (int v[]);
int find_line (int v[], int pos);

take arrays as an input, but then you try to call int pos = find_line(start_line[],loc_key[i]); , which should take the name of an array only , as it is the name which is known by the program as an array. You can easier (in my opinion) get it, if you write both of these functions following way:

int free_pos (int* v);
int find_line (int* v, int pos);

They do the same job as your functions, but you can see that their arguments are: an int pointer (array) and an int. Then, calling the function needs only the int pointer, which in your case is start_line , and the integer loc_key[i] . If you still have problems understanding it, you could read about dynamic memory allocation of arrays, which is done as: int* arr; arr = new int[your_size]; int* arr; arr = new int[your_size]; - I think it is clearer while thinking that way.

Answer 2

#include<bits/stdc++.h>
using namespace std;
int max(int arr[],int n){
maximum=INT_MAX;
for(int i=0;i<n;i++){
if(arr[i]>maximum){
maximum=arr[i]}}
return maximum;}

int main(){
int size;
cin>>size;
for(int i=0;i<size;i++){
cin>>arr[i]}
cout<<max(arr,size);
return 0;}