10783 - Odd Sum

Odd Sum

Given a range [a, b], you are to find the summation of all the odd integers in this range. For example, the summation of all the odd integers in the range [3, 9] is 3 + 5 + 7 + 9 = 24.

Input 

There can be at multiple test cases. The first line of input gives you the number of test cases, T ( 1T100). Then T test cases follow. Each test case consists of 2 integers a and b ( 0ab100) in two separate lines.

Output 

For each test case you are to print one line of output - the serial number of the test case followed by the summation of the odd integers in the range [a, b].

Sample Input 

2
1
5
3
5

Sample Output 

Case 1: 9
Case 2: 8

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Miguel Revilla 2004-12-02 

 

Solution:

#include <stdio.h>
int main() {
    static int T, t, a, b;
    scanf("%d", &T);
    for(t = 1; t <= T; t++){
        scanf("%d%d", &a, &b);
        a = a%2 == 0 ? a+1 : a;
        b = b%2 == 0 ? b-1 : b;                     
        printf("Case %d: %d\n", t, ((a+b)/2)*((b/2 + b%2)-(a/2)));
    }
    return 0;
}