1029 Median （二分）

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int getint(){
    int res=0;
    char c=getchar();
    while(!(c>='0' && c<='9')) c=getchar();
    while(c>='0' && c<='9'){
        res=res*10+(c-'0');
        c=getchar();
    }
    return res;
}

int helper(vector<int>& num1, vector<int>& num2){
    int len1=num1.size();
    int len2=num2.size();
    int halflen=(len1+len2+1)/2;
    int left=0;
    int right=len1;
    while(left<=right){
        int mid=left+(right-left)/2;
        int n1=mid;
        int n2=halflen-mid;
        int leftmax1=(n1==0)?INT_MIN:num1[n1-1];
        int rightmin1=(n1==len1)?INT_MAX:num1[n1];
        int leftmax2=(n2==0)?INT_MIN:num2[n2-1];
        int rightmin2=(n2==len2)?INT_MAX:num2[n2];
        if(leftmax1<=rightmin2 && leftmax2<=rightmin1){
            return max(leftmax1,leftmax2);
        }
        if(leftmax1>rightmin2){
            right=mid-1;
        }else{
            left=mid+1;
        }
    }
    return -1;
}

int main(){
    int n1=getint();

    vector<int> num1(n1);
    for(int i=0;i<n1;i++){
        num1[i]=getint();
    }
    int n2=getint();
    vector<int> num2(n2);
    for(int i=0;i<n2;i++){
        num2[i]=getint();
    }
    int res=0;
    if(n1<=n2){
        res=helper(num1,num2);
    }else{
        res=helper(num2,num1);
    }
    printf("%d", res);
    return 0;
}