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  • New Skateboard

    B. New Skateboard
    time limit per test
    1 second
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    Max wants to buy a new skateboard. He has calculated the amount of money that is needed to buy a new skateboard. He left a calculator on the floor and went to ask some money from his parents. Meanwhile his little brother Yusuf came and started to press the keys randomly. Unfortunately Max has forgotten the number which he had calculated. The only thing he knows is that the number is divisible by 4.

    You are given a string s consisting of digits (the number on the display of the calculator after Yusuf randomly pressed the keys). Your task is to find the number of substrings which are divisible by 4. A substring can start with a zero.

    A substring of a string is a nonempty sequence of consecutive characters.

    For example if string s is 124 then we have four substrings that are divisible by 4: 12, 4, 24 and 124. For the string 04 the answer is three: 0, 4, 04.

    As input/output can reach huge size it is recommended to use fast input/output methods: for example, prefer to use gets/scanf/printf instead of getline/cin/cout in C++, prefer to use BufferedReader/PrintWriter instead of Scanner/System.out in Java.

    Input

    The only line contains string s (1 ≤ |s| ≤ 3·105). The string s contains only digits from 0 to 9.

    Output

    Print integer a — the number of substrings of the string s that are divisible by 4.

    Note that the answer can be huge, so you should use 64-bit integer type to store it. In C++ you can use the long long integer type and in Java you can use long integer type.

    Examples
    Input
    124
    Output
    4
    Input
    04
    Output
    3
    Input
    5810438174
    Output
    9

    http://codeforces.com/problemset/problem/628/B
    思路就是只要末尾两位数能被4整除就成,
    注意结果要用long long ,我就是在这里哇了好几次,没注意。
     1 #include <iostream>
     2 #include <cstdio>
     3 #include <cstring>
     4 #include <string>
     5 #include <algorithm>
     6 #define N 300005
     7 char s[N];
     8 int a[N];
     9 using namespace std;
    10 int main(){
    11     scanf("%s",&s);
    12     long long int node=0;
    13     int c=strlen(s);
    14     int k=0;
    15     for(int i=c-1;i>=0;i--){
    16         a[k++]=s[i]-'0';
    17         if(a[k-1]%4==0)
    18             node++;
    19     }
    20     for(int i=0;i<c-1;i++){
    21         int p=a[i]+a[i+1]*10;
    22         if(p%4==0)
    23             node=node+c-i-1;
    24 
    25     }
    26     printf("%lld",node);
    27     return 0;
    28 }


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  • 原文地址:https://www.cnblogs.com/zllwxm123/p/7229612.html
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