/* A program that takes 2 command-line parameters: non-negative integer m a=
nd the name of a file
 * containing n integers in free format. The prgram finds the longest inter=
val such that
 * mx-mn<=m, and prints the interval's start position, its end position, =
and its length,
 * where mx is the maximum number in the interval, and mn is the minimum nu=
mber in the interval.
 */
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#define MAX 10000

int main(int argc, char * argv[])
{
	FILE * fp;
	int array[MAX];
	int diff;
	int startSoFar, endSoFar, max, min, lengthSoFar;
	int startNew, endNew, lengthNew;
	int num1, num2, offset, i, j=0;

	/* Check for the correct number and order of arguments */
	if (argc != 3) {
		fprintf(stderr, "Invalid number of arguments. Usage: %s difference filena=
me.\n", argv[0]);
		exit(1);
	} else if (!isdigit(*argv[1])) {
		fprintf(stderr, "Invalid first argument. Non-negative integer required.\n=
");
		exit(2);
	} else if ((fp=fopen(argv[2], "r")) == NULL) {
		fprintf(stderr, "Unable to open file %s for reading.\n", argv[2]);
		exit(3);
	} else if (fscanf(fp, "%d", &num1) != 1) {
		fprintf(stderr, "Error reading file %s.\n", argv[2]);
		exit(4);
	} else
		diff=atoi(argv[1]);

	j++;	/* First number has been read */
	startSoFar = endSoFar = -1; lengthSoFar=0;
	startNew = endNew = -1; lengthNew=0;

	while (startSoFar == -1 && fscanf(fp, "%d", &num2) == 1) {
		j++;
		if (num1 == num2) {
			min=max=num1;
			startSoFar=j-2;
		} else {
			min = (num1<num2) ? num1 : num2;
			max = (num1>num2) ? num1 : num2;

			if (max-min <= diff)
				startSoFar=j-2;
			else
				num1=num2;
		}
	}

	if (startSoFar == -1) {
		printf("No interval was found in the file that satisfied the condition.\n=
");
		printf(" %d	%d	%d\n", startSoFar, endSoFar, lengthSoFar);
	} else {
		offset=startSoFar;	/* current difference between number's positions in =
file and in array */
		array[0]=num1;
		array[1]=num2;
		i=2;

		while (i<MAX && fscanf(fp, "%d", &array[i]) == 1) {
			/* If the number read is between min and max inclusive, just add it to t=
he interval */
			if (array[i]>=min && array[i]<=max) {
				i++;
				continue;
			} else if (array[i]>max)
				max=array[i];
			else
				min=array[i];

			/* Check if condition of difference is still satisfied */
			if (max-min <= diff) {
				i++;
				continue;
			} else {
				/* Close the current interval */
				if (lengthSoFar == 0) {		/* no prior interval */
					endSoFar=i-1+offset;
					lengthSoFar=endSoFar-startSoFar+1;
				} else {
					endNew=i-1+offset;
					lengthNew=endNew-startNew+1;
					/* Check the length of newly found interval
					 * If new one is longer, reset the start and finish to that new one */
					if (lengthNew>lengthSoFar) {
						startSoFar=startNew;
						endSoFar=endNew;
						lengthSoFar=lengthNew;
					}
					/* Move array elements to the start of the array */
					for (j=0; j<=lengthNew; j++)
						array[j]=array[i-lengthNew+j];
					offset=offset+i-lengthNew;
					i=lengthNew;
				}

				/* Not end of file. Find the start of new interval */
				j=i-1;
				if (array[i] == max) {
					min=array[i];
					while (array[i]-array[j]<=diff) {
						min = (array[j]<min) ? array[j] : min;
						j--;
					}
				} else {
					max=array[i];
					while (array[j]-array[i]<=diff) {
						max = (array[j]>max) ? array[j] : max;
						j--;
					}
				}
				startNew=j+1+offset;
				i++;
			}
		}
		printf("Last index value: i=%d\n", i);
		/* Check if the firstly found interval was ever closed of */
		if (endSoFar == -1) {
			endSoFar=i-1+offset;
			lengthSoFar=endSoFar-startSoFar+1;
		}
		printf(" %d	%d	%d\n", startSoFar, endSoFar, lengthSoFar);
	}
	return 0;
}