Example 6: Digging mines (recursive solution)

Brief description of the subject:Give a directed acyclic graph, and the weight of each node, find a weight and the largest path (starting arbitrary).

Solution ideas:This question satisfies the principle of no aftereffects and optimization, and can use dynamic programming, but I can't help but write deep search + memory, but it is essentially the same. The code is very short, the logic is also very clear, is the ordinary dfs + memory.

Code example:

#include<iostream>
#include<cstdio>
#include<vector>
using namespace std;
const int maxn = 250;
int w[maxn];
vector<int> G[maxn];
int f[maxn];
int path[maxn];
int most(int p){
	if(f[p]) return f[p];
	int ans = w[p];
	for(int j = 0;j < G[p].size();j++){
		int tmp = most(G[p][j]) + w[p];
		if(ans < tmp){
			path[p] = G[p][j];
			ans = tmp;
		}
	}
	return f[p] = ans;
}
void solve(int k){
	for(int i = 1;i <= k;i++){
		most(i);
	}
	int mi = -1,pos = 0;
	for(int i = 1;i <= k;i++){
		if(mi < f[i]){
			pos = i;
			mi = f[i];
		}
	}
	cout << pos ;
	while(path[pos]){
		cout << "-" << path[pos];
		pos = path[pos];
	}
	cout << endl;
	cout << mi << endl;
}
int main(){
	
	//freopen("123.in","r",stdin);
	
	int k;
	scanf("%d",&k);
	for(int i = 1;i <= k;i++) scanf("%d",w+i);
	int from,to;
	while(scanf("%d%d",&from,&to) != EOF && (from || to)){
		G[from].push_back(to);
	}
	solve(k);
	return 0;
}

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