Gym 101201I Postman (贪心)
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题意:有个邮递员,要送信,每次最多带 m 封信,有 n 个地方要去送,每个地方有x 封要送,每次都到信全送完了,再回去,对于每个地方,可以送多次直到送够 x 封为止。
析:一个很简单的贪心,就是先送最远的,如果送完最远的还剩下,那么就送次远的,如果不够了,那么就加上回来的距离,重新带够 m 封信,对于左半轴和右半轴都是独立的,两次计算就好。
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 <sstream> #include <list> #include <assert.h> #include <bitset> #define debug() puts("++++"); #define gcd(a, b) __gcd(a, b) #define lson l,m,rt<<1 #define rson m+1,r,rt<<1|1 #define fi first #define se second #define pb push_back #define sqr(x) ((x)*(x)) #define ms(a,b) memset(a, b, sizeof a) //#define sz size() #define pu push_up #define pd push_down #define cl clear() #define FOR(x,n) for(int i = (x); i < (n); ++i) #define freopenr freopen("in.txt", "r", stdin) #define freopenw freopen("out.txt", "w", stdout) #define pii pair<int, int> using namespace std; typedef long long LL; typedef unsigned long long ULL; typedef pair<LL, int> P; const int INF = 0x3f3f3f3f; const LL LNF = 1e18; const double inf = 1e20; const double PI = acos(-1.0); const double eps = 1e-8; const int maxn = 1000 + 10; const LL mod = 1e9 + 7; const int dr[] = {-1, 0, 1, 0}; const int dc[] = {0, 1, 0, -1}; const char *de[] = {"0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"}; 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 bool is_in(int r, int c) { return r >= 0 && r < n && c >= 0 && c < m; } struct Node{ int pos; LL val; Node(int p = 0, LL v = 0) : pos(p), val(v) { } bool operator < (const Node rhs) const{ return pos > rhs.pos; } }; Node node1[maxn], node2[maxn]; int main(){ scanf("%d %d", &n, &m); int cnt1 = 0, cnt2 = 0; for(int i = 0; i < n; ++i){ int a, b; scanf("%d %d", &a, &b); if (a < 0) node1[cnt1++] = Node(-a, b); else node2[cnt2++] = Node(a, b); } sort(node1, node1 + cnt1); sort(node2, node2 + cnt2); LL ans = 0; LL pre_left = 0; for(int i = 0; i < cnt1; ++i){ if (pre_left >= node1[i].val){ pre_left -= node1[i].val; node1[i].val = 0; continue; } node1[i].val -= pre_left; LL num = (node1[i].val - 1) / m + 1; ans += num * node1[i].pos * 2; pre_left = num * m - node1[i].val; } pre_left = 0; for (int i = 0; i < cnt2; ++i){ if (pre_left >= node2[i].val){ pre_left -= node2[i].val; node2[i].val = 0; continue; } node2[i].val -= pre_left; LL num = (node2[i].val - 1) / m + 1; ans += num * node2[i].pos * 2; pre_left = num * m - node2[i].val; } printf("%I64d\n", ans); return 0; }
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