Overview Write a C program that detects and reports on areas of brightness in th
ID: 3811138 • Letter: O
Question
Overview
Write a C program that detects and reports on areas of brightness in the night sky. You will input a portion of the night sky (from standard input) represented by an n × n grid of integers where n <= 500. Each value in the grid will indicate the detected brightness of that portion of the night sky with a 0 value indicating no light. Unfortunately the detection hardware sometimes reports erroneous values; these values will show up as negative numbers and must be filtered out prior to finding the bright spots. After preprocessing your data to filter out all of the noise (more on this below), your program must report the brightest coordinate and the brightness value for that coordinate in every 5 × 5 patch of the sky that contains no zeros. Report “(none)” if no bright spots exist. Keep in mind that bright areas may overlap, and that any bright spot should only be reported once. You should also report bright spots of the 5 × 5 areas you encounter as you scan the data in a top to bottom, left to right order.
You should preprocess your data to eliminate noise in following manner: for every negative value you encounter, average the (maximum of) 8 squares around it and replace the value with the average (rounded off to the nearest whole number; use nearbyint from math.h). If one of the surrounding squares also is negative, use the value of 0 in computing the average.
Your input will consist of a single integer s representing the size of the grid followed by s × s data values. Your output should be presented exactly like the sample run (using your name, of course, instead of mine). You also must use functions to input your data into an array, to preprocess your array, and one to find and report the bright spots. In other words you should have at least 3 separate functions defined that each are passed your two-dimensional data array where one function only inputs the array, one function only preprocesses the data to eliminate noise, and one function only finds and reports the bright spots. These functions must all be called from main. You must define your array local to your main function and pass it into all functions that need it. You may not declare and use any global data (other than possibly preprocessor definitions to define the maximum size of the sky and debugging flags if used).
Sample Run:
20
0 0 0 0 0 0 0 13 18 18 15 5 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 6 16 19 16 6 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 12 16 18 17 5 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 12 14 12 14 9 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 8 10 4 6 10 0 0 0 0 0 0
0 0 0 0 3 3 5 3 -2 10 12 11 11 6 0 0 0 0 0 0
0 0 0 0 5 6 6 6 5 7 13 14 13 4 0 0 0 0 0 0
0 0 0 0 2 7 8 6 4 8 12 13 11 9 0 0 0 0 0 0
0 0 0 0 2 7 7 7 5 9 4 10 6 4 0 0 0 -2 0 0
0 0 0 0 4 4 3 4 3 6 6 4 5 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 6 8 8 7 5 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 5 7 9 8 6 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 5 7 7 8 3 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 3 5 4 4 4 0 0 0 0 0 0 0
0 0 0 0 3 3 3 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 -1 -1 -2 8 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 -1 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Sample run using above data:
liberty Cprogs/96 qCC brightest c liberty Cprogs 96 a out brightest 4.dat Project 46; Dan Resler Grid size: 20x20 Bright spots: 9,111 14 10, 61 8 8, 9] 10 9,101 13 110,111 13 111, 111 10 [14, 101 9 liberty /cprogs/96Explanation / Answer
#include <stdio.h>
#include <math.h>
#define SIZE 500
void preprocess(int brightness[SIZE][SIZE], int n)
{
int i, j;
for(i = 0; i < n; i++)
{
for(j = 0; j < n; j++)
{
if (brightness[i][j] < 0)
{
double d = 0;
int count = 0;
// coordinate in above row
if (i - 1 >= 0)
{
d += brightness[i-1][j];
count++;
if (j -1 >= 0)
{
d+= brightness[i-1][j-1];
count++;
}
if (j + 1 < n)
{
d+= brightness[i-1][j+1];
count++;
}
}
// row just below
if (i + 1 < n)
{
d += brightness[i+1][j];
count++;
if (j - 1 >= 0)
{
d+= brightness[i+1][j-1];
count++;
}
if (j + 1 < n)
{
d+= brightness[i+1][j+1];
count++;
}
}
// coordinate just left
if (j - 1 >= 0)
{
d += brightness[i][j-1];
count++;
}
// coordinate just right
if (j + 1 < n)
{
d += brightness[i][j+1];
count++;
}
brightness[i][j] = (int)nearbyint(d/count);
}
}
}
}
int findBrightSpotInSmaller(int brightness[SIZE][SIZE], int i, int j, int *coord1, int *coord2)
{
int max = brightness[i][j];
*coord1 = i;
*coord2 = j;
int r, c;
for(r = i; r < i+5; r++)
{
for(c = j; c < j+5; c++)
{
if (brightness[r][c] == 0)
{
return -1;
}
if (brightness[r][c] > max)
{
max = brightness[r][c];
*coord1 = r;
*coord2 = c;
}
}
}
return max;
}
void findBrightSpots(int brightness[SIZE][SIZE], int n)
{
printf("Grid size: %dx%d ", n, n);
printf("Bright spots: ");
int i, j;
int reported[n][n];
for(i = 0; i < n; i++)
{
for(j = 0; j < n; j++)
{
reported[i][j] = 0;
}
}
for(i = 0; i <= n-5; i++)
{
for (j = 0; j <= n-5; j++)
{
int coord1, coord2;
int maxBright = findBrightSpotInSmaller(brightness, i, j, &coord1, &coord2);
if (maxBright != -1)
{
if(reported[coord1][coord2] != 1)
{
printf("[%d,%d] %d ", coord1, coord2, maxBright);
reported[coord1][coord2] = 1;
}
}
}
}
}
int inputBrightness(int brightness[SIZE][SIZE])
{
int n;
scanf("%d", &n);
int i, j;
for(i = 0; i < n; i++)
{
for(j = 0; j < n; j++)
{
scanf("%d", &brightness[i][j]);
}
}
return n;
}
int main()
{
printf("Poject #6; Your name ");
int brightness[SIZE][SIZE];
int n = inputBrightness(brightness);
preprocess(brightness, n);
findBrightSpots(brightness, n);
return 0;
}
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