HDU 4509 湫湫系列故事——减肥记II(线段树)

#include <iostream>
#include <cstdio>
using namespace std;
#define lson l, m, rt << 1
#define rson m + 1, r, rt << 1 | 1
const int maxn = 1441;

int segs[maxn << 2], f[maxn << 2], n;
void build(int l, int r, int rt){
segs[rt] = 0;
f[rt] = 0;
if(l == r)return;
int m = (l + r) >> 1;
build(lson),build(rson);
}
void pushDown(int l, int r, int rt){
if(f[rt]){
int m = (l + r) >> 1;
f[rt << 1] = f[rt << 1 | 1] = 1;
segs[rt << 1] = m - l + 1;
segs[rt << 1 | 1] = r - m;
f[rt] = 0;
}
}
void pushUp(int rt){
segs[rt] = segs[rt << 1] + segs[rt << 1 | 1];
}
void update(int L, int R, int l, int r, int rt){
if(L <= l && r <= R){
f[rt] = 1;
segs[rt] = r - l + 1;
return ;
}
pushDown(l, r, rt);
int m = (l + r) >> 1;
if(L <= m)update(L, R, lson);
if(R > m) update(L, R, rson);
pushUp(rt);
}
int query(int L, int R, int l, int r, int rt){
if(L <= l && r <= R){
return segs[rt];
}
pushDown(l, r, rt);
int m = (l + r) >> 1, ret = 0;
if(L <= m)ret += query(L, R, lson);
if(R > m) ret += query(L, R, rson);
pushUp(rt);
return ret;
}
int main(){
while (~scanf("%d", &n)){
build(0, maxn, 1);
while (n--){
int a1, b1, a2, b2;
scanf("%d:%d %d:%d", &a1, & b1, &a2, &b2);
int l = a1 * 60 + b1, r = a2 * 60 + b2;
if(abs(l -r) == 0)continue;
update(l, r - 1, 0, maxn, 1);
}
printf("%d\n",1440 - query(0, 1440, 1, maxn, 1));
}
return 0;
}