• Pasha and String(思维,技巧)


    Pasha and String
    Time Limit:2000MS     Memory Limit:262144KB     64bit IO Format:%I64d & %I64u

    Description

    Pasha got a very beautiful string s for his birthday, the string consists of lowercase Latin letters. The letters in the string are numbered from 1 to |s| from left to right, where |s| is the length of the given string.

    Pasha didn't like his present very much so he decided to change it. After his birthday Pasha spent m days performing the following transformations on his string — each day he chose integer ai and reversed a piece of string (a segment) from position ai to position|s| - ai + 1. It is guaranteed that ai ≤ |s|.

    You face the following task: determine what Pasha's string will look like after m days.

    Input

    The first line of the input contains Pasha's string s of length from 2 to 2·105 characters, consisting of lowercase Latin letters.

    The second line contains a single integer m (1 ≤ m ≤ 105) —  the number of days when Pasha changed his string.

    The third line contains m space-separated elements ai (1 ≤ ai; ai ≤ |s|) — the position from which Pasha started transforming the string on the i-th day.

    Output

    In the first line of the output print what Pasha's string s will look like after m days.

    Sample Input

    Input
    abcdef 1 2
    Output
    aedcbf
    Input
    vwxyz 2 2 2
    Output
    vwxyz
    Input
    abcdef 3 1 2 3
    Output
    fbdcea
    题解:
    对于一个字符串,给m个询问,每次交换从i到n-i之间的字符,由于大的区间包含小的区间,只需要求交换的总次数就好了,奇数交换对称的两个数,偶数不交换;
    代码:
    #include<iostream>
    #include<cstring>
    #include<cmath>
    #include<algorithm>
    #include<cstdio>
    using namespace std;
    const int MAXN = 2e5 + 100;
    int tree[MAXN];
    char s[MAXN];
    int main(){
        int m, x;
        while(~scanf("%s", s + 1)){
            scanf("%d", &m);
            memset(tree, 0, sizeof(tree));
            while(m--){
                scanf("%d", &x);
                tree[x]++;
            }
            int len = strlen(s +  1);
            for(int i = 2; i <= len / 2; i++){
                tree[i] += tree[i - 1];
            }
            for(int i = 1; i <= len / 2; i++){
                if(tree[i] & 1)swap(s[i], s[len - i + 1]);
            }
            printf("%s
    ",s + 1);
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/handsomecui/p/5414774.html
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