P2082 区间覆盖(加强版)

基础刷起来。水题刷起来。。。

其实区间覆盖的模板应该背这个。。。

同样维护left和right，只不过最后要加上r-l+1。里面维护的就有点不一样。

代码：

#include<cstdio>
#include<algorithm>
const int maxn = 1e5 + 5;
#define ll long long
struct Nodes
{
	ll l, r;
} s[maxn];
ll n;
bool cmp(Nodes x, Nodes y)
{
	return x.l < y.l;
}
ll read()
{
	ll ans = 0, s = 1;
	char ch = getchar();
	while(ch > '9' || ch < '0'){ if(ch == '-') s = -1; ch = getchar(); }
	while(ch >= '0' && ch <= '9') ans = (ans << 3) + (ans << 1) + ch - '0', ch = getchar();
	return s * ans;
}
int main()
{
	n = read();
	for(int i = 1; i <= n; i++) s[i].l = read(), s[i].r = read();
	std::sort(s + 1, s + n + 1, cmp);
	ll left = s[1].l, right = s[1].r;
	ll ans = 0;
	for(int i = 2; i <= n; i++)
	{
		if(right < s[i].l)
		{
			ans += right - left + 1;
			left = s[i].l; right = s[i].r;
		}
		else if(s[i].r > right)
		{
			//ans += right - left + 1;
			right = s[i].r;
		}
	}
	printf("%lld\n", ans + right - left + 1);
	return 0;
}