Description
You are given a rooted tree with n vertices. The vertices are numbered from 1 to n, the root is the vertex number 1.
Each vertex has a color, let's denote the color of vertex v by cv. Initially cv = 0.
You have to color the tree into the given colors using the smallest possible number of steps. On each step you can choose a vertex v and a color x, and then color all vectices in the subtree of v (including v itself) in color x. In other words, for every vertex u, such that the path from root to u passes through v, set cu = x.
It is guaranteed that you have to color each vertex in a color different from 0.
You can learn what a rooted tree is using the link: https://en.wikipedia.org/wiki/Tree_(graph_theory).
Input
The first line contains a single integer n (2 ≤ n ≤ 104) — the number of vertices in the tree.
The second line contains n - 1 integers p2, p3, ..., pn (1 ≤ pi < i), where pi means that there is an edge between vertices i and pi.
The third line contains n integers c1, c2, ..., cn (1 ≤ ci ≤ n), where ci is the color you should color the i-th vertex into.
It is guaranteed that the given graph is a tree.
Output
Print a single integer — the minimum number of steps you have to perform to color the tree into given colors.
Sample Input
6
1 2 2 1 5
2 1 1 1 1 1
3
7
1 1 2 3 1 4
3 3 1 1 1 2 3
5
Hint
The tree from the first sample is shown on the picture (numbers are vetices' indices):
On first step we color all vertices in the subtree of vertex 1 into color 2 (numbers are colors):
On seond step we color all vertices in the subtree of vertex 5 into color 1:
On third step we color all vertices in the subtree of vertex 2 into color 1:
The tree from the second sample is shown on the picture (numbers are vetices' indices):
On first step we color all vertices in the subtree of vertex 1 into color 3 (numbers are colors):
On second step we color all vertices in the subtree of vertex 3 into color 1:
On third step we color all vertices in the subtree of vertex 6 into color 2:
On fourth step we color all vertices in the subtree of vertex 4 into color 1:
On fith step we color all vertices in the subtree of vertex 7 into color 3:
从第二个节点开始的节点和父节点(上一个节点)相连,
例如:1 2 2 1 5
代表:节点2和节点1相连,节点3和节点2相连,节点4和节点2相连,节点5和节点1相连,节点6和节点5相连。 第三行内容是需要将各个点涂成的颜色,给这个树涂色,有这么一条原则就是给某一节点涂色,以其为根节点的子树也将变为相应的颜色,我们可以成为一种颜料的溢出,问你最终需要
最少需要涂多少次颜色就可以满足题目要求。 解题思路:我们可以这样来思考,因为最后需要使所有的点都涂成要求的颜色,一定是按照从根节点到叶子节点遍历的涂色,但所有的点都遍历会造成浪费,我们只需要找出需要涂的点即可,
那么哪些点需要涂呢?我们发现只有那些最后要求的其父亲节点和本身不同色的需要涂色,因为需要向下改变自身颜色,那么只需要统计这样点的个数即可。
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int pr[10010];
int a[10010];
int main()
{
int n,i,counts;
scanf("%d",&n);
counts=0;
pr[0]=1;
pr[1]=1;///根节点的父亲节点是自身
for(i=2;i<=n;i++)
{
scanf("%d",&pr[i]);
}
for(i=1;i<=n;i++)
{
scanf("%d",&a[i]);
}
for(i=1;i<=n;i++)
{
if(a[i]!=a[pr[i]])///父亲节点和自身颜色不同
{
counts++;
}
}
printf("%d\n",counts);
return 0;
}