In C, evaluate logical AND chain with pre-increments: what is the output?
#include
int main()
{
int i = -3, j = 2, k = 0, m;
m = ++i && ++j && ++k;
printf("%d, %d, %d, %d
", i, j, k, m);
return 0;
}
-
A-2, 3, 1, 1
-
B2, 3, 1, 2
-
C1, 2, 3, 1
-
D3, 3, 1, 2
-
E-2, 2, 0, 0
Answer
Correct Answer: -2, 3, 1, 1
Explanation
Introduction / Context:This problem targets the evaluation order and short-circuiting of the logical AND operator in C. With &&, evaluation stops at the first operand that is false (zero). If all are true (nonzero), all subexpressions are evaluated, and the final result is 1.
Given Data / Assumptions:
- i = -3, j = 2, k = 0.
- Pre-increment (++var) increments before use and yields the incremented value.
- Any nonzero value is true in C.
Concept / Approach:Check each incremented value in left-to-right order. As long as each increments to a nonzero value, the chain continues. If all are true, m becomes 1. The variables will reflect their pre-incremented values.
Step-by-Step Solution:++i: i becomes -2 → nonzero → true; continue.++j: j becomes 3 → nonzero → true; continue.++k: k becomes 1 → nonzero → true; chain completes.m = 1. Final: i = -2, j = 3, k = 1, m = 1.
Verification / Alternative check:Replace && with bitwise & to see all subexpressions evaluated regardless of truth, but note the semantic difference. With && as here, behavior matches our step-by-step trace.
Why Other Options Are Wrong:(b), (c), (d) show incorrect initial values or impossible increments. (e) contradicts the increments and truth evaluation.
Common Pitfalls:Forgetting that negative numbers are true. Also, mixing up ++i (pre-increment) with i++ (post-increment) can lead to wrong conclusions.
Final Answer:-2, 3, 1, 1