FILE* fid;
double tempx, tempy;

fid = fopen("c:/file.txt","rt");
int i=0;
while( fscanf(fid,"%le%le", &tempx, &tempy )!= EOF )
	i++;
rewind( fid );

x = new double[i];
y = new double[i];

i=0;
while (fscanf(fid,"%le%le", x+i, y+i)!= EOF)
	i++;
fclose(fid);

std::vector<int> x;
std::vector<int> y;

while(...)
{
  x.push_back(...);
  y.push_back(...);
}

#include <stdio.h>
#include <stdlib.h>

int main(void) {
    char **s = 0, **p;
    char line[BUFSIZ];
    int x, lines = 0;

    while(fgets(line, sizeof(line), stdin)) {
        p = realloc(s, sizeof(char *) * (lines+1));
        if(!p) {
            perror("Out of memory");
            exit(1);
        }
        s = p;

        s[lines] = malloc(strlen(line)+1);
        strcpy(s[lines++], line);
    }

    for(x = 0; x < lines; x ++) {
        printf("%i: %s", x, s[x]);
        free(s[x]);
    }
    free(s);

    return 0;
}