codeforces #336 div 2 B. Hamming Distance Sum

Posted by 111qqz on Wednesday, December 23, 2015

TOC

http://codeforces.com/contest/608/problem/B
题意:给定两个字符串a,b,问b中的每个连续的长度为a的子串与a的哈密顿距离的和是多少。哈密顿距离是对应位置的字符的差的绝对值的和。由于是01串,也就是字符不同的位置数。
思路:类似前缀和。0和1分别搞。注意开long long

/* ***********************************************
Author :111qqz
Created Time :2015年12月24日 星期四 00时32分33秒
File Name :code/cf/#336/B.cpp
************************************************ */

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <cmath>
#include <cstdlib>
#include <ctime>
#define fst first
#define sec second
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define ms(a,x) memset(a,x,sizeof(a))
typedef long long LL;
#define pi pair < int ,int >
#define MP make_pair

using namespace std;
const double eps = 1E-8;
const int dx4[4]={1,0,0,-1};
const int dy4[4]={0,-1,1,0};
const int inf = 0x3f3f3f3f;
const int N=3E5+7;
int la,lb;
char a[N],b[N];
int sum0[N],sum1[N];
int main()
{
    #ifndef  ONLINE_JUDGE 
    freopen("code/in.txt","r",stdin);
  #endif
    ms(sum0,0);
    ms(sum1,0);
    scanf("%s",a);
    scanf("%s",b);
    la = strlen(a);
    lb = strlen(b);
    int sum = 0 ;
    if (la==1)
    {
        for ( int i = 0 ;  i < lb ; i++)
        {
        if (b[i]!=a[0]) sum++;
        }
        cout<<sum<<endl;
        return 0;

    }
	
    for ( int i = 0 ; i < lb ; i++)
    {
        if (b[i]=='0')
        {
        sum0[i+1] = sum0[i]+1;
        sum1[i+1] = sum1[i];
        }
        else
        {
        sum1[i+1] = sum1[i] +1;
        sum0[i+1] = sum0[i];
        }
    }
//	for ( int i = 1 ; i <= lb ; i++)
//	    cout<<sum0[i]<<" "<<sum1[i]<<endl;
    LL ans =  0;
    for (int i= 0 ;  i < la ; i++)
    {
        if (a[i]=='0')
        {
        ans+=LL(sum1[lb-la+i+1]-sum1[i]);
        }
        else
        {
        ans+=LL(sum0[lb-la+i+1]-sum0[i]);
        }
//	    cout<<ans<<endl;
    }

    cout<<ans<<endl;

  #ifndef ONLINE_JUDGE  
  fclose(stdin);
  #endif
    return 0;
}

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