Click here to download density4.c.

#include "si204.h"

int main() {
  // Get target density from the user
  double target;
  fputs("Desired population density (people per sq mile): ", stdout);
  target = readnum(stdin);

  // variables for the best state and its density.
  cstring best_state;
  double best_density;
  double best_distance;
  strcpy(best_state, "ERROR");
  best_density = -100.0;
  // stores the difference between the target and best_state's density
  best_distance = target + 100.0;

  // Open data file pop.txt
  stream popin = fopen("pop.txt", "r");

  // Read in (and ignore!) the beginning with the header line
  // and overall USA population data
  { // start a block so we can declare variables locally!
    cstring garbage; // this will be used to read over unwanted data
    // count how many words need to be ignored in the header
    int initial_ignore = (3+11) + 2 + (1+11) + (4+11);
    for (int i=0; i < initial_ignore; ++i) {
      readstring(garbage, popin);
    }
  }

  // Loop over each state
  // there are 50 states + DC and PR
  for (int statenum=0; statenum < 52; ++statenum) {
    /*****************************/
    /* Process that state's info */
    /*****************************/
    cstring state;
    double density;
    cstring garbage; // this will be used to read over unwanted data

    readstring(state, popin);

    // add to state name until we see the word "Population"
    readstring(garbage, popin);
    while (strcmp(garbage, "Population") != 0) {
      strcat(state, " ");
      strcat(state, garbage);
      readstring(garbage, popin);
    }

    // second line: 11 values
    for (int i=0; i<11; ++i) {
      readstring(garbage, popin);
    }

    // third line: 4 words, 10 unwanted values, then the density
    for (int i=0; i<14; ++i) {
      readstring(garbage, popin);
    }
    density = readnum(popin);

    // fourth line: 2 words, 11 values
    for (int i=0; i<13; ++i) {
      readstring(garbage, popin);
    }

    /**************************************/
    /* Determine if this state is closest */
    /**************************************/
    double distance;
    if (density < target) {
      distance = target - density;
    } else {
      distance = density - target;
    }

    if (distance < best_distance) {
      // update the best state to this state
      strcpy(best_state, state);
      best_density = density;
      best_distance = distance;
    }
  }

  // Close the data file
  fclose(popin);

  // print out the name of the closest state
  fputs("You should live in ", stdout);
  fputs(best_state, stdout);
  fputs(" with ", stdout);
  writenum(best_density, stdout);
  fputs(" people per square mile.\n", stdout);

  return 0;
}