题目链接：https://codeforces.com/contest/1253/my
题目大意：

m个天线，每个天线的位置是xi，分数是si,覆盖范围是[xi−si;xi+si],每个硬币可以使一个天线的si+1，求覆盖整个[1;m]的最少硬币

思路：

#include <bits/stdc++.h>
using namespace std;
const int N = 200100;
int f[N],s[N],x[N];
int main()
{
    int n,m;
    cin >> n >> m;
    for (int i = 1; i <= m; i++){
        f[i]=1<<30;
    }
    f[0] = 0;
    for (int i = 1; i <= n; i++)
    {
        cin >> x[i] >> s[i];
    }
    for (int i = 1; i<= m; i++){
        for (int j = 1; j <= n;j++){
            if ( i >= x[j])
            {
                f[i] = min(f[i],f[max(2*x[j]-i-1,0)]+max(i-x[j]-s[j],0));
                f[i] = min(f[i], max(2*x[j]-i-1,0)+max(i-x[j]-s[j],0));
            }
            else
            {
                f[i] = min(f[i],f[max(x[j]-s[j]-1,0)]);
                f[i] = min(f[i],max(x[j]-s[j]-1,0));
            }
        }
    }
    cout << f[m] << endl;

    return 0;
}