题目描述
思路
尽量不要直接使用getchar得到单个字符，容易出现runtime error， 可以使用scanf("%s", str), 直接判断str[0]是否是对应字符就可以了。
代码
#include <cstdio>
#include <cstring>
#define lc k<<1
#define rc k<<1|1
const int MAX = 100100;
int n, m, wt[MAX], ans;
int head[MAX], ver[MAX << 1], nt[MAX << 1], ht;
int fa[MAX], size[MAX], son[MAX], dep[MAX];
int top[MAX], dfn[MAX], tr[MAX], dt;
int lg[MAX << 2], rg[MAX << 2], sum[MAX << 2];
bool fg[MAX << 2];
char str[100];
int read() {
int s = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch > '9') {
if (ch == '-') f = -1;
ch = getchar();
}
while (ch >= '0' && ch <= '9') {
s = s * 10 + ch - '0'; ch = getchar();
}
return s * f;
}
void write(int x) {
if (x > 9) write(x / 10);
putchar(x % 10 + '0');
}
void add(int x, int y) {
nt[++ht] = head[x], head[x] = ht, ver[ht] = y;
}
void dfs1(int x, int u) {
fa[x] = u;
dep[x] = dep[u] + 1;
size[x] = 1;
for (int i = head[x], j; j = ver[i]; i = nt[i]) {
if (j == u) continue;
dfs1(j, x);
size[x] += size[j];
if (size[j] > size[son[x]]) son[x] = j;
}
}
void dfs2(int x, int u) {
top[x] = u;
dfn[x] = ++dt;
tr[dt] = x;
if (son[x]) dfs2(son[x], u);
for (int i = head[x], j; j = ver[i]; i = nt[i]) {
if (!dfn[j]) dfs2(j, j);
}
}
void pushup(int k, int l, int r) {
lg[k] = lg[lc], rg[k] = rg[rc];
sum[k] = sum[lc] + sum[rc];
if (rg[lc] == lg[rc]) sum[k]--;
}
void pushdown(int k, int l, int r, int mid) {
if (!fg[k]) return;
fg[lc] = fg[rc] = true;
sum[lc] = sum[rc] = 1;
lg[lc] = lg[rc] = rg[lc] = rg[rc] = lg[k];
fg[k] = false;
}
void swap(int &x, int &y) {
int t = x;
x = y, y = t;
}
void build(int k, int l, int r) {
if (l == r) {
lg[k] = rg[k] = wt[tr[l]];
sum[k] = 1;
return;
}
int mid = l + r >> 1;
build(lc, l, mid);
build(rc, mid + 1, r);
pushup(k, l, r);
}
int getColor(int k, int l, int r, int x) {
if (l == r && x == l) return lg[k];
int mid = l + r >> 1;
pushdown(k, l, r, mid);
if (x <= mid) return getColor(lc, l, mid, x);
else return getColor(rc, mid + 1, r, x);
}
void change(int k, int l, int r, int x, int y, int z) {
if (x <= l && r <= y) {
fg[k] = true;
sum[k] = 1;
lg[k] = rg[k] = z;
return;
}
int mid = l + r >> 1;
pushdown(k, l, r, mid);
if (x <= mid) change(lc, l, mid, x, y, z);
if (y > mid) change(rc, mid + 1, r, x, y, z);
pushup(k, l, r);
}
void query(int k, int l, int r, int x, int y) {
if (x <= l && r <= y) {
ans += sum[k];
return;
}
int mid = l + r >> 1;
pushdown(k, l, r, mid);
if (x <= mid) query(lc, l, mid, x, y);
if (y > mid) query(rc, mid + 1, r, x, y);
if (x <= mid && y > mid && rg[lc] == lg[rc]) ans--;
}
void ask(int x, int y) {
int fx = top[x], fy = top[y];
while (fx != fy) {
if (dep[fx] < dep[fy]) swap(x, y), swap(fx, fy);
query(1, 1, n, dfn[fx], dfn[x]);
if (getColor(1, 1, n, dfn[fx]) == getColor(1, 1, n, dfn[fa[fx]])) ans--;
x = fa[fx], fx = top[x];
}
if (dep[x] > dep[y]) swap(x, y);
query(1, 1, n, dfn[x], dfn[y]);
}
void askChange(int x, int y, int z) {
int fx = top[x], fy = top[y];
while (fx != fy) {
if (dep[fx] < dep[fy]) swap(x, y), swap(fx, fy);
change(1, 1, n, dfn[fx], dfn[x], z);
x = fa[fx], fx = top[x];
}
if (dep[x] > dep[y]) swap(x, y);
change(1, 1, n, dfn[x], dfn[y], z);
}
int main() {
n = read(), m = read();
for (int i = 1; i <= n; ++i) wt[i] = read();
for (int i = 1, a, b; i < n; ++i) {
a = read(), b = read();
add(a, b), add(b, a);
}
dfs1(1, 0);
dfs2(1, 1);
build(1, 1, n);
for (int i = 1, j, a, b, c; i <= m; ++i) {
scanf("%s", str);
if (str[0] == 'Q') {
a = read(), b = read();
ans = 0;
ask(a, b);
write(ans);
puts("");
} else {
a = read(), b = read(), c = read();
askChange(a, b, c);
}
}
return 0;
}