服了,搞半天,原来是我long存的数据太小,不得不用BigIntger了。 alt

        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
//            long a = sc.nextLong();
//            long b = sc.nextLong();
//            long c = sc.nextLong();
            BigInteger a = new BigInteger(sc.next());
            BigInteger b = new BigInteger(sc.next());
            BigInteger c = new BigInteger(sc.next());
            if (isTriangle(a, b, c)) {
                System.out.println("Yes");
            } else {
                System.out.println("No");
            }
        }
    }

    public static boolean isTriangle(BigInteger a, BigInteger b, BigInteger c) {
//        return a + b > c && a + c > b && b + c > a;
        return a.add(b).compareTo(c) > 0 && a.add(c).compareTo(b) > 0 && b.add(c).compareTo(a) > 0;
    }

alt