[Link] https://AtCoder.jp/contests/abc237/tasks/abc237_e
Consider the following apth: Space 0 => Space x Path: upper, lower distance: U, D => happiness: D - 2 * U => To maximize happiness : minimize U => PriorityQue
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import java.util.*;
import java.io.*;
public class Main {
static BufferedReader br;
static StringBuilder sb = new StringBuilder();
static int[] h;
public static void main(String[] args) throws IOException {
br = new BufferedReader(new InputStreamReader(System.in));
int[] arr = getArr();
int n = arr[0], m = arr[1];
ArrayList<ArrayList<Integer>> al = new ArrayList<>();
for(int i = 0; i < n; i++) al.add(new ArrayList<Integer>());
h = getArr();
for(int i = 0; i < m; i++) {
arr = getArr();
int a = arr[0] - 1, b = arr[1] - 1;
al.get(a).add(b);
al.get(b).add(a);
}
PriorityQueue<Edge> pq = new PriorityQueue<>((l, r) -> Long.compare(l.elevate, r.elevate));
long max = 0;
boolean[] visit = new boolean[n];
long[] dijk = new long[n];
Arrays.fill(dijk, Long.MIN_VALUE);
dijk[0] = 0;
pq.add(new Edge(0, 0, 0));
while(!pq.isEmpty()) {
Edge edge = pq.poll();
if(visit[edge.to]) continue;
visit[edge.to] = true;
for(int e: al.get(edge.to)) {
if(visit[e]) continue;
if(h[e] >= h[edge.to]) {
if(dijk[e] > dijk[edge.to] + getVal(edge.to, e)) continue;
dijk[e] = dijk[edge.to] + getVal(edge.to, e);
pq.add(new Edge(edge.to, e, edge.elevate + h[e] - h[edge.to]));
if(dijk[e] > max) max = dijk[edge.to];
} else {
if(dijk[e] > dijk[edge.to] + getVal(edge.to, e)) continue;
dijk[e] = dijk[edge.to] + getVal(edge.to, e);
pq.add(new Edge(e, e, edge.elevate));
if(dijk[e] > max) max = dijk[e];
}
}
}
print(max);
}
static int getVal(int from, int to) {
if(h[from] == h[to]) return 0;
if(h[from] > h[to]) return h[from] - h[to];
return 2 * (h[from] - h[to]);
}
static class Edge{
int from;
int to;
long elevate;
Edge(int from, int to, long elevate) {
this.from = from;
this.to =to;
this.elevate = elevate;
}
}
static int toi(String s) { return Integer.parseInt(s); }
static String[] getLine() throws IOException { return br.readLine().split(" "); }
static int[] getArr() throws IOException { return Arrays.stream(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); }
static <T> void print(T s) { System.out.print(s); }
static <T> void println(T s) { System.out.println(s); }
}