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I'm new to C programming. I came across this problem in codechef.
https://www.codechef.com/problems/TLG?tab=statement
I have no idea why it is failing. Please help.
The game of billiards involves two players knocking 3 balls around on a green baize table. Well, there is more to it, but for our purposes this is sufficient.
The game consists of several rounds and in each round both players obtain a score, based on how well they played. Once all the rounds have been played, the total score of each player is determined by adding up the scores in all the rounds and the player with the higher total score is declared the winner.
The Siruseri Sports Club organises an annual billiards game where the top two players of Siruseri play against each other. The Manager of Siruseri Sports Club decided to add his own twist to the game by changing the rules for determining the winner. In his version, at the end of each round, the cumulative score for each player is calculated, and the leader and her current lead are found. Once all the rounds are over the player who had the maximum lead at the end of any round in the game is declared the winner.
Consider the following score sheet for a game with 5 rounds:
Round
Player 1
Player 2
1
140
82
2
89
134
3
90
110
4
112
106
5
88
90
The total scores of both players, the leader and the lead after each round for this game is given below:
Round
Player 1
Player 2
Leader
Lead
1
140
82
Player 1
58
2
229
216
Player 1
13
3
319
326
Player 2
7
4
431
432
Player 2
1
5
519
522
Player 2
3
Note that the above table contains the cumulative scores.
The winner of this game is Player 1 as he had the maximum lead (58 at the end of round 1) during the game.
Your task is to help the Manager find the winner and the winning lead. You may assume that the scores will be such that there will always be a single winner. That is, there are no ties.
Input
The first line of the input will contain a single integer N (N ≤ 10000) indicating the number of rounds in the game. Lines 2,3,...,N+1 describe the scores of the two players in the N rounds. Line i+1 contains two integer Si and Ti, the scores of the Player 1 and 2 respectively, in round i. You may assume that 1 ≤ Si ≤ 1000 and 1 ≤ Ti ≤ 1000.
Output
Your output must consist of a single line containing two integers W and L, where W is 1 or 2 and indicates the winner and L is the maximum lead attained by the winner.
Sample 1:
Input:
5
140 82
89 134
90 110
112 106
88 90
Output:
1 58
My code:
#include <stdio.h>
#include <stdlib.h>
int main(void) {
int N, a, b, cum1 = 0, cum2 = 0, lead = 0, leader = 0;
scanf("%d", &N);
while (N--) {
scanf("%d%d", &a, &b);
cum1 += a;
cum2 += b;
if (abs(cum1 - cum2) > lead) {
lead = abs(cum1 - cum2);
leader = cum1 > cum2 ? 1 : 2;
}
}
printf("%d%d\n", leader, lead);
return 0;
}
I tried solving it without the use of array, but it is showing as wrong answer. Unfortunately I don't know the failed test cases either. What can be the reasons for such failure?

Answer 1

There is at least this problem: you print both numbers without a space in between. The printf statement should be changed to:
printf("%d %d\n", leader, lead);
You should have been able to diagnose this problem by running your program with sample test data on your system or with an online compiler with a shell window. Testing and debugging are a must for programming, you must learn these skills early.
Aside from this trivial problem, your code is elegant and simple, the use of arrays is definitely not warranted.
Yet there is a non obvious limitation that might be a problem on some systems: both N and all Si and Ti values are specified with a range that will fit in type int, but the cumulative scores might exceed 32767, which is the largest value the int type may handle in some older 16-bit systems. For maximum portability, you should use type long, function labs() and the %ld conversion specifier.
Here is a modified version with extra sanity checks:
#include <stdio.h>
#include <stdlib.h>
int main(void) {
int N, a, b, leader = 0;
long cum1 = 0, cum2 = 0, lead = 0;
if (scanf("%d", &N) != 1)
return 1;
while (N-- > 0 && scanf("%d%d", &a, &b) == 2) {
cum1 += a;
cum2 += b;
if (labs(cum1 - cum2) > lead) {
lead = labs(cum1 - cum2);
leader = cum1 > cum2 ? 1 : 2;
}
}
printf("%d %ld\n", leader, lead);
return 0;
}