BZOJ3523 [Poi2014]Bricks 【贪心】

题目链接

题解

简单的贪心题

优先与上一个不一样且数量最多的，如果有多个相同，则优先选择非结尾颜色

比较显然，但不知怎么证

#include<algorithm>

#include<iostream>

#include<cstring>

#include<cstdio>

#include<queue>

#include<cmath>

#include<map>

#define Redge(u) for (int k = h[u],to; k; k = ed[k].nxt)

#define REP(i,n) for (int i = 1; i <= (n); i++)

#define mp(a,b) (cp){a,b}

#define cls(s) memset(s,0,sizeof(s))

#define LL long long int

using namespace std;

const int maxn = 1000005,maxm = 100005,INF = 1000000000;

inline int read(){

	int out = 0,flag = 1; char c = getchar();

	while (c < 48 || c > 57){if (c == '-') flag = -1; c = getchar();}

	while (c >= 48 && c <= 57){out = (out << 3) + (out << 1) + c - 48; c = getchar();}

	return out * flag;

}

int ans[maxn],n,s,t,m;

struct cp{

	int cnt,id;

};

inline bool operator <(const cp& a,const cp& b){

	return a.cnt == b.cnt ? a.id != t : a.cnt < b.cnt;

}

priority_queue<cp> q;

int main(){

	n = read(),s = read(),t = read();

	if (n == 1 && (s != t)){puts("0"); return 0;}

	int tmp;

	REP(i,n){

		tmp = read(); m += tmp;

		if (i == s) tmp--;

		if (i == t) tmp--;

		if (tmp == -1){puts("0"); return 0;}

		if (tmp) q.push(mp(tmp,i));

	}

	cp u,v;

	ans[1] = s; ans[m] = t;

	for (int i = 2; i < m; i++){

		u = q.top(); q.pop();

		if (u.id == ans[i - 1]){

			if (q.empty()){puts("0"); return 0;}

			v = q.top(); q.pop();

			ans[i] = v.id; v.cnt--;

			q.push(u);

			if (v.cnt) q.push(v);

		}

		else {

			ans[i] = u.id; u.cnt--;

			if (u.cnt) q.push(u);

		}

	}

	if (ans[m - 1] == t){puts("0"); return 0;}

	for (int i = 1; i <= m; i++)

		printf("%d ",ans[i]);

	return 0;

}

巴特西

BZOJ3523 [Poi2014]Bricks 【贪心】

题目链接

题解

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