題目鏈接：http://codeforces.com/problemset/problem/545/C

題目：

Little Susie listens to fairy tales before bed every day. Today‘s fairy tale was about wood cutters and the little girl immediately started imagining the choppers cutting wood. She imagined the situation that is described below.

There are n

The first line contains integer n (1 ≤ n ≤ 105) — the number of trees.

Next n lines contain pairs of integers xi, hi (1 ≤ xi, hi ≤ 109) — the coordinate and the height of the ?-th tree.

The pairs are given in the order of ascending xi. No two trees are located at the point with the same coordinate.

Print a single number — the maximum number of trees that you can cut down by the given rules.

5
1 2
2 1
5 10
10 9
19 1

3

5
1 2
2 1
5 10
10 9
20 1

4

In the first sample you can fell the trees like that:

• fell the 1-st tree to the left — now it occupies segment [ - 1;1]
• fell the 2-nd tree to the right — now it occupies segment [2;3]
• leave the 3-rd tree — it occupies point 5
• leave the 4-th tree — it occupies point 10
• fell the 5-th tree to the right — now it occupies segment [19;20]

In the second sample you can also fell 4-th tree to the right, after that it will occupy segment [10;19].

題解：貪心 ，能放就盡可能放。

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 
 4 const int N=1e5+10;
 5 int x[N],h[N];
 6 
 7 int main(){
 8     int n,ans=0;
 9     scanf("%d",&n);
10     for(int i=1;i<=n;i++) scanf("%d%d",&x[i],&h[i]);
11     x[0]=-2e9-10;x[n+1]=2e9+10;
12     for(int i=1;i<=n;i++){
13         if((x[i]-h[i])>x[i-1]) ans++;
14         else if((x[i]+h[i])<x[i+1]){
15             ans++;
16             x[i]=x[i]+h[i];
17         }
18     }
19     printf("%d\n",ans);
20     return 0;
21 }

CF 545C Woodcutters（貪心）