// CSE 373, Winter 2013, Marty Stepp
// This program performs some operations and
// measures and reports the total runtime.
// It forms a basis for runtime efficiency testing.

import java.util.*;

/* alg 1
 * 3200		1848
 * 6400		15296
 *
 * alg 2
 * 51200	522
 * 102400	2109
 * 204800	8928
 *
 */

public class Lecture04 {
	public static void main(String[] args) {
		// perform a timing test for arrays of increasing size (doubling every
		// time)
		System.out.println("N\tTime (ms)");
		for (int n = 100; n <= 100000000; n = n * 2) {
			timingTest(n);
		}
	}

	// Computes on a randomly generated array of the given size.
	public static void timingTest(int size) {
		// create an array of random data with a mixture of positive and
		// negative values
		int[] a = new int[size];
		Random rand = new Random();
		for (int i = 0; i < a.length; i++) {
			a[i] = rand.nextInt(1001) - 500;
		}

		// get start/stop system times to find out how fast the code ran
		long startTime = System.currentTimeMillis();

		// WRITE THE CODE TO TIME HERE
		int max = maxSum1(a);

		long endTime = System.currentTimeMillis();

		System.out.println(size + "\t" + (endTime - startTime));
	}

	public static int maxSum1(int[] a) {
		int max = 0;
		int sum = 0;
		int i = 0;
		for (int j = 0; j < a.length; j++) {
			if (sum < 0) { // if sum becomes negative, max range
				i = j; // cannot start with any of i - j-1,
				sum = 0; // (Claim 2) so move i up to j
			}
			sum += a[j];
			if (sum > max) {
				max = sum;
			}
		}
		return max;
	}
}