P3842 [TJOI2007]线段(线性dp)

[TJOI2007]线段 - 洛谷icon-default.png?t=M276https://www.luogu.com.cn/problem/P3842

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
const int MN = 65005;
const int MAXN = 2000010;
const int INF = 0x3f3f3f3f;
#define IOS ios::sync_with_stdio(false)


int n;
int l[MAXN], r[MAXN];
int dp[MAXN][2];
int main() {
	scanf("%d", &n);
	for (int i = 1; i <= n; i++) {
		scanf("%d %d", l + i, r + i);
	}
	dp[1][0] = r[1] - 1 + r[1] - l[1];
	dp[1][1] = r[1] - 1;
	for (int i = 2; i <= n; i++) {
		dp[i][0] = min(1 + dp[i - 1][0] + abs(l[i - 1] - r[i]) + r[i] - l[i],
		               1 + dp[i - 1][1] + abs(r[i - 1] - r[i]) + r[i] - l[i]);
		dp[i][1] = min(1 + dp[i - 1][0] + abs(l[i - 1] - l[i]) + r[i] - l[i],
		               1 + dp[i - 1][1] + abs(r[i - 1] - l[i]) + r[i] - l[i]);
	}
	printf("%d", min(dp[n][0] + n - l[n], dp[n][1] + n - r[n]));
	return 0;
}

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