POJ.1769 Minimizing maximizer

1.Problem
http://poj.org/problem?id=1769

2.Idea
DP + Segtree

3.Source

 int n, m;  
 int s[MAX_M], t[MAX_M];  
 int dp[MAX_N + 1];  
 void solve()  
 {  
      rmq_init(n);  
      fill(dp, dp + n + 1, INF);  
      dp[1] = 0;  
      update(1, 0);  
      for (int i = 0; i < m; i++) {  
           int v = min(dp[t[i]], query(s[i], t[i] + 1) + 1);  
           dp[t[i]] = v;  
           update(t[i], v);  
      }  
      printf("%d\n", dp[n]);  
 }