http://acm.hdu.edu.cn/showproblem.php?pid=5124

題意：區間覆蓋次數問題。

解題思路：線段樹水之。

#include<iostream> #include<cstdio> #include<cstring> #include<algorithm> using namespace std;const int maxn = 100005; struct Node {int x,y; }p[maxn]; struct Seg {int l,r,Max,lazy; }tree[maxn<<2]; int n,tot,cnt,tmp[maxn<<1],order[maxn];void build(int rt,int l,int r) {tree[rt].l = l, tree[rt].r = r;tree[rt].Max = 0,tree[rt].lazy = 0;if(l == r) return;int mid = (l + r) >> 1;build(rt<<1,l,mid);build(rt<<1|1,mid+1,r); }void PushDown(int rt) {if(tree[rt].lazy){tree[rt<<1].lazy += tree[rt].lazy;tree[rt<<1].Max += tree[rt].lazy;tree[rt<<1|1].lazy += tree[rt].lazy;tree[rt<<1|1].Max += tree[rt].lazy;tree[rt].lazy = 0;} }void update(int rt,int l,int r) {if(l <= tree[rt].l && tree[rt].r <= r){tree[rt].Max++;tree[rt].lazy++;return;}PushDown(rt);int mid = (tree[rt].l + tree[rt].r) >> 1;if(l <= mid) update(rt<<1,l,r);if(mid < r) update(rt<<1|1,l,r);tree[rt].Max = max(tree[rt<<1].Max,tree[rt<<1|1].Max); }int bisearch(int k) {int l = 1, r = cnt, mid;while(l <= r){mid = (l + r) >> 1;if(order[mid] == k) return mid;else if(order[mid] < k)l = mid + 1;else r = mid - 1;} }int main() {int t;scanf("%d",&t);while(t--){tot = cnt = 0;scanf("%d",&n);for(int i = 1; i <= n; i++){scanf("%d%d",&p[i].x,&p[i].y);tmp[tot++] = p[i].x;tmp[tot++] = p[i].y;}sort(tmp,tmp+tot);order[++cnt] = tmp[0];for(int i = 1; i < tot; i++)if(tmp[i] != tmp[i-1])order[++cnt] = tmp[i];build(1,1,cnt);for(int i = 1; i <= n; i++){int l = bisearch(p[i].x);int r = bisearch(p[i].y);update(1,l,r);}printf("%d\n",tree[1].Max);}return 0; }

總結

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