#include<bits/stdc++.h>
using namespace std;
const int Base=100000000,Len=8,N=10004;
int a[N],b[N],la,lb;
int Two(int x[],int&len){
	if(x[1]%2){
		return 0;
	}
	for(int i=len;i>=1;i--){
		x[i-1]+=x[i]%2*Base;
		x[i]/=2;
	}
	if(x[len]==0){
		len--;
	}
	return Two(x,len)+1;
}
int Cmp(int x[],int y[]){//a>b
	if(la!=lb){
		return la>lb?1:-1;
	}
	for(int i=la;i>=1;i--){
		if(x[i]>y[i]){
			return 1;
		}
		if(x[i]<y[i]){
			return -1;
		}
	}
	return 0;
}
void Sub(int x[],int&lx,int y[],int&ly){
	for(int i=1;i<=ly;i++){
		x[i]-=y[i];
	}
	for(int i=1;i<=ly;i++){
		if(x[i]<0){
			x[i]+=Base;
			x[i+1]--;
		}
	}
	while(x[lx]==0&&lx>1){
		lx--;
	}
}
void Mul(int x[],int&lx,int v){
	for(int i=1;i<=lx;i++){
		x[i]*=v;
	}
	for(int i=1;i<=lx;i++){
		x[i+1]+=x[i]/Base;
		x[i]%=Base;
	}
	while(x[lx+1]!=0){
		lx++;
	}
}
string s1,s2;
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>s1>>s2;
	reverse(s1.begin(),s1.end());
	reverse(s2.begin(),s2.end());
	la=s1.size(),lb=s2.size();
	for(int i=1;i<=la;i++){
		a[(i-1)/Len+1]+=(s1[i-1]-'0')*pow(10,(i-1)%Len);
	}
	for(int i=1;i<=lb;i++){
		b[(i-1)/Len+1]+=(s2[i-1]-'0')*pow(10,(i-1)%Len);
	}
	la=(la-1)/Len+1;
	lb=(lb-1)/Len+1;
	int Pow=min(Two(a,la),Two(b,lb));
	while(1){
		int res=Cmp(a,b);
		if(res==1){
			Sub(a,la,b,lb);
			Two(a,la);
		}
		else if(res==-1){
			Sub(b,lb,a,la);
			Two(b,la);
		}
		else{
			break;
		}
	}
	for(int i=1;i<=Pow;i++){
		Mul(a,la,2);
	}
	for(int i=la;i>=1;i--){
		if(i!=la){
			printf("%08d",a[i]);
		}
		else{
			printf("%d",a[i]);
		}
	}
	return 0;
}

这份TLE。

#include<bits/stdc++.h>
using namespace std;

int vbase = 100000000;
int vcnt = 8;
int a[100010];
int lena;
int b[100010];
int lenb;

int two(int x[], int& len) {
    if (x[1] % 2) {
        return 0;
    }
    for (int i = len; i >= 1; i--) {
        x[i - 1] += x[i] % 2 * vbase;
        x[i] /= 2;
    }
    if (x[len] == 0) {
        len--;
    }
    return two(x, len) + 1;
}

bool equal(int x[], int y[]) {
    if (lena != lenb) {
        return false;
    }
    for (int i = 1; i <= lena; i++) {
        if (x[i] != y[i]) {
            return false;
        }
    }
    return true;
}

int cmp(int x[], int y[]) {
    if (lena != lenb) {
        return lena > lenb ? 1 : -1;
    }
    for (int i = lena; i >= 1; i--) {
        if (x[i] > y[i]) {
            return 1;
        }
        if (x[i] < y[i]) {
            return -1;
        }
    }
    return 0;
}

void sub(int x[], int& lenx, int y[], int& leny) {
    for (int i = 1; i <= leny; i++) {
        x[i] -= y[i];
    }
    for (int i = 1; i <= leny; i++) {
        if (x[i] < 0) {
            x[i] += vbase;
            x[i + 1]--;
        }
    }
    while (x[lenx] == 0 && lenx > 1) {
        lenx--;
    }
}

void mul(int x[], int& lenx, int v) {
    for (int i = 1; i <= lenx; i++) {
        x[i] *= v;
    }

    for (int i = 1; i <= lenx; i++) {
        x[i + 1] += x[i] / vbase;
        x[i] %= vbase;
    }
    while (x[lenx + 1] != 0) {
        lenx++;
    }
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    string s1, s2;
    cin >> s1 >> s2;
    std::reverse(s1.begin(), s1.end());
    std::reverse(s2.begin(), s2.end());
    lena = s1.size();
    lenb = s2.size();
    for (int i = 1; i <= lena; i++) {
        a[(i - 1) / vcnt + 1] += (s1[i-1] - '0') * pow(10, (i - 1) % vcnt);
    }
    for (int i = 1; i <= lenb; i++) {
        b[(i - 1) / vcnt + 1] += (s2[i-1] - '0') * pow(10, (i - 1) % vcnt);
    }
    lena = (lena - 1) / vcnt + 1;
    lenb = (lenb - 1) / vcnt + 1;

    int power = min(two(a, lena), two(b, lenb));
    while (1) {
        int res = cmp(a, b);
        if (res == 1) {
            sub(a, lena, b, lenb);
            two(a, lena);
        }
        else if (res == -1) {
            sub(b, lenb, a, lena);
            two(b, lenb);
        }
        else {
            break;
        }
    }

    for (int i = 1; i <= power; i++) {
        mul(a, lena, 2);
    }

    for (int i = lena; i >= 1; i--) {
        if (i != lena) {
            printf("%08d", a[i]);
        }
        else {
            printf("%d", a[i]);
        }
    }

    return 0;
}

这份AC