B. Swap and Delete

合集 - codeforces(57)

1.C. Insert and Equalize2023-12-062.C. Removal of Unattractive Pairs2023-12-063.D. Jumping Through Segments2023-12-084.E. Good Triples2023-12-085.F. Shift and Reverse2023-12-086.D. Yet Another Monster Fight2023-12-117.A. Constructive Problems2023-12-188.C. Game with Multiset2023-12-199.A. Rating Increase2023-12-19

10.B. Swap and Delete2023-12-19

11.A. Problemsolving Log2023-12-2012.B. Preparing for the Contest2023-12-2013.C. Quests2023-12-2014.D. Three Activities2023-12-2015.E2. Game with Marbles (Hard Version)2023-12-2016.cf刷题有感2023-12-2017.A. Anonymous Informant2023-12-2118.A. Forked!2023-12-2319.B. Make Almost Equal With Mod2023-12-2720.C. Heavy Intervals2023-12-2721.D. Split Plus K2023-12-2822.A. 20232023-12-3123.B. Two Divisors2023-12-3124.C. Training Before the Olympiad2023-12-3125.D. Mathematical Problem2024-01-0226.F. Greetings2024-01-0227.C. Partitioning the Array2024-01-1528.G. Bicycles2024-01-1629.E. Eat the Chip2024-01-1730.G. Lights2024-01-1731.D. Array Repetition2024-01-1732.D. Berserk Monsters2024-01-2233.E. Increasing Subsequences2024-01-2334.D. Very Different Array2024-01-2435.G. Mischievous Shooter2024-01-2536.B. Plus-Minus Split2024-01-2737.B. A Balanced Problemset2024-01-2838.C. Did We Get Everything Covered2024-01-2839.D. Find the Different Ones!2024-02-0840.C. Grouping Increases2024-02-1041.D. Good Trip2024-02-1242.C. Physical Education Lesson2024-02-1243.E. Final Countdown2024-02-1844.D. Divisible Pairs2024-02-1945.G. Vlad and Trouble at MIT2024-02-2046.A. Brick Wall2024-02-2847.B. Minimize Inversions2024-02-2848.C. XOR-distance2024-02-2849.A. Moving Chips2024-02-2850.B. Monsters Attack!2024-02-2851.C. Find B2024-02-2852.D. Slimes2024-02-2853.C. Turtle Fingers: Count the Values of k2024-02-2854.D. Turtle Tenacity: Continual Mods2024-02-2855.D. Vlad and Division2024-02-2856.C. LR-remainders2024-02-2857.D. Lonely Mountain Dungeons2024-03-12

收起

原题链接

反思 要明确每个变量的含义！！！

读题

1.取一对01置换，或者删掉一个元素，使得经过若干次改变后的序列$t$，和$s$的前$|t|$项元素各不相同。求问最少要删掉几个元素？

一些事实的思考

1.对于一个给定的序列$a$，和另一个 “0的个数”与“1的个数”均相同，但是排列不同的 序列b，能否经过有限次01置换使b变成a？
答案是可以的。具体请参考线性代数中逆序数的介绍，看完你就明白了。

2.截取$s$的前$|k|$段为$s1$，设$s1$含0的个数为$a$，含1的个数为$b$，则对应的$t$需要$a$个1，$b$个0。

思路

1.线性循环，计算当前状态含01的个数，和达到当前状态时减去01的个数，有多少个零->就需要保留多少个1->就需要减去多少个1
2.如果需要1或0的个数不够了，说明达不到当前状态，后面状态也一定达不到，退出。

代码

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin>>n;
    while(n--)
    {
        string s;
        cin>>s;
        int a=0,b=0;
        for(int i=0;s[i];i++)
            if(s[i]=='1')a++;
            else b++;


        int ans=a+b;
        int a1=0,b1=0;
        for(int i=0;s[i];i++)
        {
            if(s[i]=='1')b1++;
            else a1++;
            if(a1>a||b1>b)break;
            ans=min(ans,a+b-a1-b1);//总数减去需要保留的个数
        }
        cout<<ans<<endl;
    }
    return 0;
}