Merge pull request #852 from simranquirky/master

Red alert solution (codechef problem) in C language.

Author: smv1999

Codechef Problems/Red_alert.c

@@ -0,0 +1,106 @@
+/* PROBLEM STATEMENT 
+
+
+Finally a monsoon has come. According to the Meteorological Department, there will be rain in the upcoming N days in the city. Initially, the water level of the city is zero millimetres. The amount of rain on the i-th day can be described by an integer Ai as follows:
+
+If Ai>0, the water level of the city increases by Ai millimetres on the i-th day.
+If Ai=0, there is no rain on the i-th day. The water level of the city decreases by D millimetres on such a day. However, if the water level is less than D millimetres before the i-th day, then it becomes zero instead.
+There will be a red alert in the city if the water level becomes strictly greater than H millimetres on at least one of the N days. Determine if there will be a red alert.
+
+Input Format
+The first line of the input contains a single integer T denoting the number of test cases. The description of T test cases follows.
+The first line of each test case contains three space-separated integers N, D and H.
+The second line contains N space-separated integers A1,A2,…,AN.
+Output Format
+For each test case, print a single line containing the string "YES" if there will be a red alert or "NO" otherwise.
+
+Constraints
+1≤T≤103
+1≤N,D≤102
+0≤Ai≤102 for each valid i
+1≤H≤104
+Subtasks
+Subtask #1 (100 points): original constraints
+
+Sample Input 1 
+4
+4 2 6
+1 3 0 2
+2 1 100
+1 100
+4 2 3
+1 2 0 2
+3 7 10
+5 3 9 
+Sample Output 1 
+NO
+YES
+NO
+YES
+Explanation
+Example case 1:
+
+On the first day, the water level of the city increases to 1 millimtre.
+On the second day, the water level increases by 3 millimeters and becomes 1+3=4 millimtres.
+On the third day, there is no rain in the city, so the water level decreases by D=2 millimtres and becomes 4−2=2 millimtres.
+On the fourth day, the water level increases by 2 millimtres and becomes 2+2=4 millimtres.
+There will be no red alert in the city because the water level does not exceed H=6 millimtres on any of the four days.
+
+Example case 2: The water level of the city on the 2-nd day is equal to 101 millimtres, which is greater than H=100 millimtres, so there will be a red alert in the city.
+
+Example case 3: The water levels of the city on the four days are [1,3,1,3]. The water level is equal to H=3 millimtres on the second and fourth day, but it does not exceed the threshold.
+
+Example case 4: There will be a red alert in the city on the 3-rd day.  */
+
+// SOLUTION
+
+#include <stdio.h>
+
+int main(void) {
+	
+	int t,n,d,h;
+	
+	scanf("%d",&t);
+	// t represents the number of test cases
+
+	 while(t--) //the loop runs for t times 
+	 {
+	     	scanf("%d %d %d",&n,&d,&h);
+		 // n, d and h respectively stores the input values
+	     	int sum=0;int val; int ret=0;
+	     	for(int i=0;i<n;i++) // this loop take n values as user input
+	     	{
+			
+	     	    scanf("%d",&val); // the values inputted are stored each time in the variable val
+			//note: here a single variable is used instead of an array beacuse the operations are done on the variable here itself i.e. within this loop.
+	     	    if(val>0)
+	     	    {
+			    //if val( the level of water on ith day > 0
+	     	        sum+=val; // total level = previous(stored in sum itsef) + val;
+	     	       
+	     	    }
+	     	    if(val==0)
+	     	    {
+			    //if val( the level of water on ith day = 0
+	     	        sum=(sum<d)?0 : (sum-d);
+	     	       // the ternary operator above checks if sum<d for true: sum =0 for false: sum-d
+	     	    }
+			
+	     	     if(sum>h) //checks the level each day (level is calculated by carrying out arithmetic operations on variable val which is finally stored in variable sum
+	     	        {
+	     	            ret=1; //if red alert  i.e. sum > h , the variable ret is initialised with value 1.
+			     break; 
+	     	        }
+	     	}
+	     	if(ret==0) 
+	     	printf("NO\n");
+	     	else 
+	     	printf("YES\n");
+	     	// Time Complexity : O(N)
+		 // Space Complexity: 0(1)
+	     	
+	 }
+	 
+	
+	return 0;
+}