codeforce Gym 100500F Door Lock （二分）

根据题意略推一下，其实就是问你满足(a*(a+1))/2 < m <= ((a+1)*a(a+2))/2的a和m-(a*(a+1))/2 -1是多少。

二分求解就行了

#include<cstdio>using namespace std;
typedef long long ll;int main()
{int T;scanf("%d",&T);for(int k = 1; k <= T; k++){ll n,m;scanf("%I64d%I64d",&n,&m);ll L = 0, R = n;ll mid , b1, b2;while(L < R){mid = (L + R) >> 1;b1 = (mid*(mid+1))>>1;if(m <= b1) {R = mid;continue;}b2 = ((mid+2)*(mid+1))>>1;if(b2 < m) {L = mid;continue;}break;}if(L == R) mid = L;printf("Case %d: %I64d %I64d\n",k,mid,m-b1-1);}return 0;
}