WA 30：

extern "C" int Seniorious(int x);
extern "C" int Chtholly(int n,int c){
	int l = 1, r = n;
	while(1){
		int mid = (l + r) / 2;
		if (Seniorious(mid) == 1) r = mid-1;
		if (Seniorious(mid) == -1) l = mid+1;
		if (Seniorious(mid) == 0) return mid;
	}
}

AC 100：

extern "C" int Seniorious(int x);
extern "C" int Chtholly(int n,int c){
	int l = 1, r = n;
	while(1){
		int mid = (l + r) / 2;
		int res = Seniorious(mid);
		if (res == 1) r = mid-1;
		if (res == -1) l = mid+1;
		if (res == 0) return mid;
	}
}

为什么把函数返回值存到变量里就 AC 了 QAQ