Templates for XCPC - Misc

Misc

常用常数

#define INF 0x3f3f3f3f
#define LLINF 0x3f3f3f3f3f3f3f3f

取消输入输出流同步

inline void fastio(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
}

二分查找边界

while(l<r){
    int mid=(l+r)/2;
    if(check(mid))r=mid;
    else l=mid+1;
}
while(l<r){
    int mid=(l+r+1)/2;
    if(check(mid))l=mid;
    else r=mid-1;
}

三分求函数最大值

const double eps=1e-7;
double f(double x){
    //...
}
int main(){
    cin>>N>>l>>r;
    for(int i=N;i>=0;i--)cin>>a[i];
    while(r-l>eps){
        double mid=(l+r)/2;
        double lmid=mid-eps,rmid=mid+eps;
        if(f(lmid)>f(rmid))r=mid;
        else l=mid;
    }
    printf("%.5f",l);
    return 0;
}