PAT A1065 A+B and C (64bit) (20point(s))

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Given three integers A, B and C in [−263, 263], you are supposed to tell whether A+B>C.

Input Specification:

The first line of the input gives the positive number of test cases, T (≤10). Then T test cases follow, each consists of a single line containing three integers A, B and C, separated by single spaces.

Output Specification:

For each test case, output in one line Case #X: true if A+B>C, or Case #X: false otherwise, where X is the case number (starting from 1).

Sample Input:

3
1 2 3
2 3 4
9223372036854775807 -9223372036854775808 0

Sample Output:

Case #1: false
Case #2: true
Case #3: false

题意

给出长度为8字节的三个数A,B,C,判断A+B>C是否为真。

解答

显然,A,B,C在long long范围内,因此可以定义为long long变量,这里主要是考虑两种溢出情况:

  1. 负数+负数,A+B为正数或0时溢出(当A,B都是char类型时,-128+(-128)=0,long long类型也类似)
  2. 正数+正数,A+B为负数时溢出,A+B不会等于0
#include<iostream>
using namespace std;
int main()
{
	int n;
	long long a, b, c;
	bool cmp;
	scanf("%d", &n);
	for (int i = 0; i < n; i++) {
		scanf("%lld %lld %lld", &a, &b, &c);
		long long tmp = a + b;
		if (a > 0 && b > 0 && tmp < 0) cmp = true;
		else if (a < 0 && b < 0 && tmp >= 0) cmp = false;
		else if (tmp > c) cmp = true;
		else cmp = false;
		if (cmp) printf("Case #%d: true\n", i + 1);
		else printf("Case #%d: false\n", i + 1);
	}
	return 0;
}