HDU 1698 Just a Hook——区间更新的线段树

来源：互联网发布：微信软文制作软件编辑：程序博客网时间：2024/06/11 10:15

题意：一开始有n个1组成的数列，执行q此操作，每次操作给出x y z，表示把区间【x，y】内的所有数变成z，执行完q此操作后求整个数列的和

思路：直接套用区间更新线段树的模板，进行简单的更新值与求和操作

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;const int maxn = 1e5 + 10;int T, n, q, date[maxn], segTree[maxn<<2], lazy[maxn<<2];void init() {    for (int i = 1; i <= n; i++) {        date[i] = 1;    }    for (int i = 1; i <= n<<2; i++) {        segTree[i] = 0;        lazy[i] = 0;    }}void pushup(int root) {    segTree[root] = segTree[root<<1] + segTree[root<<1|1];}void pushdown(int root, int cntL, int cntR) {    if (lazy[root]) {        lazy[root<<1] = lazy[root];        lazy[root<<1|1] = lazy[root];        segTree[root<<1] = lazy[root] * cntL;        segTree[root<<1|1] = lazy[root] * cntR;        lazy[root] = 0;    }}void build(int L, int R, int root) {    if (L == R) {        segTree[root] = date[L];        return;    }    int mid = (L + R)>>1;    build(L, mid, root<<1);    build(mid + 1, R, root<<1|1);    pushup(root);}void update_interval(int L, int R, int root, int uL, int uR, int val) {    if (uL <= L && R <= uR) {        segTree[root] = val * (R - L + 1);        lazy[root] = val;        return;    }    int mid = (L + R)>>1;    pushdown(root, mid - L + 1, R - mid);    if (uL <= mid) {        update_interval(L, mid, root<<1, uL, uR, val);    }    if (uR > mid) {        update_interval(mid + 1, R, root<<1|1, uL, uR, val);    }    pushup(root);}int query(int L, int R, int root, int qL, int qR) {    if (qL <= L && R <= qR) {        return segTree[root];    }    int mid = (L + R)>>1;    pushdown(root, mid - L + 1, R - mid);    int ans = 0;    if (qL <= mid) {        ans += query(L, mid, root<<1, qL, qR);    }    if (qR > mid) {        ans += query(mid + 1, R, root<<1|1, qL, qR);    }    return ans;}int main(){    scanf("%d", &T);    for (int kase = 1; kase <= T; kase++) {        scanf("%d%d", &n, &q);        init();        build(1, n, 1);        while (q--) {            int a, b, c; scanf("%d %d %d", &a, &b, &c);            update_interval(1, n, 1, a, b, c);        }        printf("Case %d: The total value of the hook is %d.\n", kase, query(1, n, 1, 1, n));    }    return 0;}

阅读全文

1 0