P1622 释放囚犯 （区间dp）

 原题链接：释放囚犯 - 洛谷

AC代码： 

#include<bits/stdc++.h>
#define INF 0x3f3f3f3f
#define ll long long
#define PII pair<int,int>
#define rep(i, n) for (int i = 1; i <= (n); ++i)
#define rrep(i, n) for(int i = n; i >= 1; ++i)

using namespace std;

const double pi = acos(-1.0);

const int N = 1010;
int a[N], s[N], b[N];
int f[N][N];
int n, m;
int main()
{
    scanf("%d %d", &n, &m);
    rep(i, m) scanf("%d", &a[i]);
    m++;
    a[m] = n + 1;
    rep(i, m) b[i] = a[i] - a[i - 1] - 1;
    rep(i, m) s[i] = s[i - 1] + b[i];
    for(int len = 2; len <= m; len++)
        for(int i = 1; i + len - 1 <= m; i++)
    {
        int j = i + len - 1;
        f[i][j] = INF;
        for(int k = i; k < j; k++)
        f[i][j] = min(f[i][j], f[i][k] + f[k + 1][j] + s[j] - s[i - 1] + j - i - 1);
    }
    printf("%d", f[1][m]);
    return 0;
}