C++14(g++5.4) 解法, 执行用时: 4ms, 内存消耗: 404K, 提交时间: 2020-08-05 23:38:45

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
ll d1, d2, w1, w2;
ll l[5], r[5];
ll get(ll n, ll num){
	return (2 * n - num + 1) * num;
}
void solve(ll n, ll m, int id){
	r[id] = 2 * m / n + 1 - n; r[id] /= 2;
	ll L, R, mid;
	if((n + 1) * n > 2 * m){
		L = 0; R = n;
		while(R - L > 1){
			mid = (L + R) / 2;
			if(get(mid, mid) <= 2 * m) L = mid;
			else R = mid;
		}
	}///0-n
	else{
		L = n, R = 1e10;
		while(R - L > 1){
			mid = (L + R) / 2;
			if(get(mid, n) <= 2 * m) L = mid;
			else R = mid;
		}
	}///n-无穷
	l[id] = L;
	while((2 * r[id] + n - 1) * n >= 2 * m) r[id]--;
	while((2 * r[id] + n - 1) * n < 2 * m) r[id]++;
	swap(l[id], r[id]);
	if(l[id] < 0) l[id] = 0;
}
void print(int id){
	printf("l = %lld  r = %lld\n", l[id], r[id]);
}
int main(){
	scanf("%lld%lld%lld%lld", &d1, &d2, &w1, &w2);
	solve(d1, w1, 1);
	solve(d2, w2, 2);
	//print(1); print(2);
	if(l[1] > r[1] || l[2] > r[2] || l[1] < 0 || r[1] < 0 || l[2] < 0 || r[2] < 0){
		puts("Impossible");
	}
	else{
		l[1]--; r[1]++;
		if(l[1] < 0) l[1] = 0;
		if(r[1] < 0) r[1] = 0;
		if(l[2] > r[1] || r[2] < l[1]){
			puts("Impossible");
		}
		else{
			puts("Possible");
		}
	}
	return 0;
}

C++11(clang++ 3.9) 解法, 执行用时: 4ms, 内存消耗: 616K, 提交时间: 2020-03-24 22:44:58

#include<bits/stdc++.h>

using namespace std;

int d1, d2, w1, w2;
int main(){
    scanf("%d%d%d%d", &d1, &d2, &w1, &w2);
    long long t1 = 1ll*(d1-1)*d1/2, t2 = 1ll*(d2-1)*d2/2;
    long long a = max(0ll, (w1-t1+d1-1)/d1);
    long long b = max(0ll, (w2-t2+d2-1)/d2);
    long long c, d;
    if(w1 < t1) c = static_cast<int>(sqrt(2.0*w1+0.25)-0.5);
    else c = 1ll*(w1+t1)/d1;
    if(w2 < t2) d = static_cast<int>(sqrt(2.0*w2+0.25)-0.5);
    else d = 1ll*(w2+t2)/d2;
    if(max(a,b)-min(c,d) <= 1) puts("Possible");
    else puts("Impossible");
    return 0;
}