Kirinriki

Posted on | In , ,

题目链接

题意

定义两个字符串
现在给出$S$，问从其中挑出两个不重叠的子串，$dis$小于$m$，最长长度是多少。

思路

枚举对称轴，然后划框。主要是个思维题，想到了就没什么可说的。

Code

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#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#ifndef ONLINE_JUDGE
#define dbg(x...) do{cout << "\033[33;1m" << #x << "->" ; err(x);} while (0)
void err(){cout << "\033[39;0m" << endl;}
template<template<typename...> class T, typename t, typename... A>
void err(T<t> a, A... x){for (auto v: a) cout << v << ' '; err(x...);}
template<typename T, typename... A>
void err(T a, A... x){cout << a << ' '; err(x...);}
#else
#define dbg(...)
#endif
#define inf 1ll << 50

const int N = 5e3 + 5;
char s[N];

int main()
{
    int T;
    scanf("%d", &T);
    while (T--)
    {
        int m;
        scanf("%d", &m);
        int ans = 0;
        scanf("%s", s);
        int len = strlen(s);
        for (int i = 0; i < len; i++)
        {
            int sum = 0;
            int head = i, tail = i - 1;
            while (tail <= len - 2 && 2 * i - tail - 1 > 0)
            {
                tail++;
                sum += abs(s[tail] - s[2 * i - tail - 1]);
                while (head <= tail && sum > m)
                {
                    sum -= abs(s[head] - s[2 * i - head - 1]);
                    head++;
                }
                ans = max(ans, tail - head + 1);
            }
        }
        for (int i = 1; i < len - 1; i++)
        {
            int sum = 0;
            int head = i + 1, tail = i;
            while (tail <= len - 2 && 2 * i - tail > 0)
            {
                tail++;
                sum += abs(s[tail] - s[2 * i - tail]);
                while (head <= tail && sum > m)
                {
                    sum -= abs(s[head] - s[2 * i - head]);
                    head++;
                }
                ans = max(ans, tail - head + 1);
            }
        }
        printf("%d\n", ans);
    }
    return 0;
}
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