(PAT 1065) A+B and C (64bit) (整数溢出问题)-蒲公英云

(PAT 1065) A+B and C (64bit) (整数溢出问题)

Given three integers A, B and C in [−2^63,2^63], 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, Band 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

解题思路:

整数相加溢出问题

如果两个正数相加结果<=0,则发生了溢出

如果两个负数相加结果>=0,则发生了溢出

如果正数发生了溢出,那么它们相加一定比结果要大,如果负数发生了溢出,那么它们相加一定比结果要小

分情况讨论即可

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
int main() {
    int N;
    bool flag = false;
    scanf("%d", &N);
    long long a, b, c;
    for (int i = 0; i < N; ++i) {
        scanf("%lld %lld %lld", &a, &b, &c);
        long long res = a + b;
        if (a > 0 && b > 0 && res <= 0) {
            flag = true;
        }
        else if (a < 0 && b < 0 && res >= 0) {
            flag = false;
        }
        else {
            if (a + b > c) {
                flag = true;
            }
            else {
                flag = false;
            }
        }
        if (flag) {
            printf("Case #%d: true\n", i + 1);
        }
        else {
            printf("Case #%d: false\n", i + 1);
        }
    }
    system("PAUSE");
    return 0;
}