题意:有n个垃圾,第i个垃圾坐标为(xi,yi),重量为wi,有一个机器人,要按照编号从小到大的顺序剑气所有的垃圾兵扔进垃圾桶,垃圾桶在原点,
每次总重量不能超过C,两点间距离为曼哈顿距离,求出最短的距离和。
析:第一反应想到的状态是有个数和重量,一看,时间复杂度受不了,只能改。dp[i] 表示从原点出发倒掉前 i 个垃圾,并放到垃圾桶所要的最短距离。
dp[i] = min{dp[j] + dist(j+1, i) + disttoorigin(i) + disttoorigin(j+1)} j <= i w(j+i, i) <= C 其中dist(j+1, i) 表示第 j+1 个垃圾到第 i 个
垃圾的距离,disttoorigin(i) 表示第 i 个垃圾到原点的距离,w(i, j) 表示第 i-j个垃圾的总重量。 dist disttoorigin 都可以预处理出来。
dist(j, i) = totaldist(i) - totaldist(j)。dp[i] = min{fun[j] |w(j+1, i) <= C} + totaldist(i) + disttoorigin(i)。
fun[j] = dp[j] - totaldist(j+1) + disttoorigin(j+1),我们只要维护fun[i]最小就好了,所以就要维护一个单调队列。
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 <unordered_map> #include <unordered_set> #define debug() puts("++++"); #define freopenr freopen("in.txt", "r", stdin) #define freopenw freopen("out.txt", "w", stdout) using namespace std; typedef long long LL; typedef pair<int, int> P; const int INF = 0x3f3f3f3f; const double inf = 0x3f3f3f3f3f3f; const double PI = acos(-1.0); const double eps = 1e-8; const int maxn = 1e5 + 5; const int mod = 2000; const int dr[] = {-1, 1, 0, 0}; const int dc[] = {0, 0, 1, -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; } int x[maxn], y[maxn], w[maxn]; int sum[maxn], sumw[maxn]; int q[maxn], dist[maxn]; int dp[maxn]; inline int func(int i){ return dp[i] - sum[i+1] + dist[i+1]; } int main(){ int T; cin >> T; while(T--){ scanf("%d %d", &m, &n); x[0] = y[0] = w[0] = sum[0] = sumw[0] = 0; for(int i = 1; i <= n; ++i){ scanf("%d %d %d", x+i, y+i, w+i); dist[i] = abs(x[i]) + abs(y[i]); sum[i] = sum[i-1] + abs(x[i] - x[i-1]) + abs(y[i] - y[i-1]); sumw[i] = sumw[i-1] + w[i]; } int front = 1, rear = 1; q[1] = 0; for(int i = 1; i <= n; ++i){ while(front <= rear && sumw[i] - sumw[q[front]] > m) ++front; dp[i] = func(q[front]) + dist[i] + sum[i]; while(front <= rear && func(i) <= func(q[rear])) --rear; q[++rear] = i; } printf("%d\n", dp[n]); if(T) puts(""); } return 0; }