代码

#include <cstdio>#include <cstring>#include <iostream>#define N 1001#define min(x, y) ((x) < (y) ? (x) : (y))int n, s;int f[N][N][2], a[N], d[N];inline int read(){	int x = 0, f = 1;	char ch = getchar();	for(; !isdigit(ch); ch = getchar()) if(ch == ‘-‘) f = -1;	for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - ‘0‘;	return x * f;}int main(){	int i, j;	n = read();	s = read();	for(i = 1; i <= n; i++) d[i] = read(), a[i] = read() + a[i - 1];	memset(f, 127 / 3, sizeof(f));	f[s][s][0] = f[s][s][1] = 0;	for(i = s; i >= 1; i--)		for(j = i + 1; j <= n; j++)		{			f[i][j][0] = min(f[i][j][0], f[i + 1][j][0] + (d[i + 1] - d[i]) * (a[n] - (a[j] - a[i])));			f[i][j][0] = min(f[i][j][0], f[i + 1][j][1] + (d[j] - d[i]) * (a[n] - (a[j] - a[i])));			f[i][j][1] = min(f[i][j][1], f[i][j - 1][0] + (d[j] - d[i]) * (a[n] - (a[j - 1] - a[i - 1])));			f[i][j][1] = min(f[i][j][1], f[i][j - 1][1] + (d[j] - d[j - 1]) * (a[n] - (a[j - 1] - a[i - 1])));		}	printf("%d\n", min(f[1][n][0], f[1][n][1]));	return 0;}