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为什么用指针就可以对,用变量模拟指针就会WA呢?

Posted by litble at 2017-08-14 21:23:24 on Problem 1635
诚恳地求大神帮助,感激不尽!QAQ
我是用hash实现本题的,但是一直都WA,于是我找了别人的代码来看,这样就可以AC:
#include<algorithm>
#include<iostream>
#include<cstring>
#include<climits>
#include<cstdio>
using namespace std;
int T,t;
char s[2][3100],l1,l2;
char *p;
int h1,h2,hx[11000];
int has(int dep){
	int re=hx[dep+5000];
	while(*p&&*p++=='0')//指针模拟,实现递归
		re=(re+hx[dep]*has(dep+1))%19001;//计算每棵子树的hash值
	return re*re%19001;
}
void init(){for(int i=0;i<=10000;++i)hx[i]=rand()%19901;}//随机一些hash种子
int main()
{
    scanf("%d",&T);init();
    while(T--){
    	scanf("%s%s",s[0],s[1]);
    	p=s[0];h1=has(1);p=s[1];h2=has(1);
    	if(h1==h2)puts("same");
    	else puts("different");
    }
    return 0;
}
我原来的WA代码是这么写的:
#include<algorithm>
#include<iostream>
#include<cstring>
#include<climits>
#include<cstdio>
using namespace std;
int T,t;
char s[2][3100],l1,l2;
int h1,h2,hx[11000];
int has(int x,int dep,int l){
	int re=hx[dep+5000];
	while(t<l&&s[x][t++]=='0')//用全局变量t实现移动,只有这里和上一份代码不同
		re=(re+hx[dep]*has(x,dep+1,l))%19001;
	return re*re%19001;
}
void init(){for(int i=0;i<=10000;++i)hx[i]=rand()%19901;}
int main()
{
    init();
    scanf("%d",&T);
    while(T--){
    	scanf("%s%s",s[0],s[1]);
    	l1=strlen(s[0]),l2=strlen(s[1]);
    	t=0,h1=has(0,1,l1),t=0,h2=has(1,1,l2);
    	if(h1==h2)puts("same");
    	else puts("different");
    }
    return 0;
}

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