Ultraviolet A 1292-Strategic game

Ultraviolet A 1292-Strategic game

A tree is provided. When a node is selected, all the edges connected to it can be overwritten.


Solution: first, the rootless tree is converted into a rootless tree, and 0 is the root.
D [I] [0] indicates the minimum number of nodes required to overwrite the subtree with node I as the root when node I is not selected, d [I] [1] indicates the minimum number of nodes required to overwrite the subtree with node I as the root when node I is selected. If node I is not selected, In order to overwrite all nodes connected to node I, each son must be selected. If node I is selected, each son should select a smaller value. Recurrence by DFS order.
State transition equation:

D [I] [0] = sum {d [u] [1]} (u is the son of I)
D [I] [1] = sum {min {d [u] [0], d [u] [1]} + 1 (u is the son of I)
 

#include 
  
   #include #include 
   
    using namespace std;vector 
    
      node[1550];int n, DP[1550][2], vis[1550];void init() {    for (int i = 0; i <= n; i++) {        node[i].clear();        DP[i][0] = DP[i][1] = 0;        vis[i] = 0;    }    int x, y, num;    for (int i = 0; i < n; i++) {        scanf("%d:(%d)", &x, &num);        for (int j = 0; j < num; j++) {            scanf("%d", &y);            node[x].push_back(y);            node[y].push_back(x);        }    }}void DPS(int root) {    vis[root] = 1;    int num = node[root].size();    for (int i = 0 ; i < num; i++) {        int child = node[root][i];        if (vis[child])            continue;        DPS(child);        DP[root][0] += DP[child][1];        DP[root][1] += min(DP[child][0], DP[child][1]);    }    DP[root][1]++;}int main() {    while (scanf("%d", &n) != EOF) {        init();        DPS(0);        printf("%d\n", min(DP[0][0], DP[0][1]));    }    return 0;}