CodeForces 722C Destroying Array (并查集)

题意：给定 n 个数，然后每次破坏一个位置的数，那么剩下的连通块的和最大是多少。

析：用并查集来做，从后往前推，一开始什么也没有，如果破坏一个，那么我们就加上一个，然后判断它左右两侧是不是存在，如果存在，那么就合并起来，

然后不断最大值，因为这个最大值肯定是不递减，所以我们一直更新就好。

代码如下：

#pragma comment(linker, "/STACK:1024000000,1024000000")

#include <cstdio>

#include <string>

#include <cstdlib>

#include <cmath>

#include <iostream>

#include <cstring>

#include <set>

#include <queue>

#include <algorithm>

#include <vector>

#include <map>

#include <cctype>

#include <cmath>

#include <stack>

//#include <tr1/unordered_map>

#define freopenr freopen("in.txt", "r", stdin)

#define freopenw freopen("out.txt", "w", stdout)

using namespace std;

//using namespace std :: tr1;

typedef long long LL;

typedef pair<int, int> P;

const int INF = 0x3f3f3f3f;

const double inf = 0x3f3f3f3f3f3f;

const LL LNF = 0x3f3f3f3f3f3f;

const double PI = acos(-1.0);

const double eps = 1e-8;

const int maxn = 1e5 + 5;

const LL mod = 10000000000007;

const int N = 1e6 + 5;

const int dr[] = {-1, 0, 1, 0, 1, 1, -1, -1};

const int dc[] = {0, 1, 0, -1, 1, -1, 1, -1};

const char *Hex[] = {"0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"};

inline LL gcd(LL a, LL b){  return b == 0 ? a : gcd(b, a%b); }

int n, m;

const int mon[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

const int monn[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

inline int Min(int a, int b){ return a < b ? a : b; }

inline int Max(int a, int b){ return a > b ? a : b; }

inline LL Min(LL a, LL b){ return a < b ? a : b; }

inline LL Max(LL a, LL b){ return a > b ? a : b; }

inline bool is_in(int r, int c){

    return r >= 0 && r < n && c >= 0 && c < m;

}

int a[maxn], b[maxn], p[maxn];

bool num[maxn];

vector<LL> ans;

LL ran[maxn];

int Find(int x) {  return x == p[x] ? x : p[x] = Find(p[x]); }

int main(){

    while(scanf("%d", &n) == 1){

        for(int i = 1; i <= n; ++i){  scanf("%d", a+i); p[i] = i; }

        for(int i = 1; i <= n; ++i)  scanf("%d", b+i);

        ans.clear();

        memset(num, false, sizeof num);

        LL cnt = 0;

        for(int i = n; i > 0; --i){

            ans.push_back(cnt);

            int x = b[i];

            num[x] = true;

            ran[x] = a[x];

            if(num[x+1]){

                int y = Find(x+1);

                p[y] = x;

                ran[x] += ran[y];

            }

            if(num[x-1]){

                int y = Find(x-1);

                p[y] = x;

                ran[x] += ran[y];

            }

            cnt = Max(cnt, ran[x]);

        }

        for(int i = ans.size()-1; i >= 0; --i)

            printf("%I64d\n", ans[i]);

    }

    return 0;

}

巴特西

CodeForces 722C Destroying Array (并查集)

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