题目：

Squirrel Liss liv

Escape from Stonesed in a forest peacefully, but unexpected trouble happens. Stones fall from a mountain. Initially Squirrel Liss occupies an interval [0, 1]. Next, n stones will fall and Liss will escape from the stones. The stones are numbered from 1 to n in order.
The stones always fall to the center of Liss's interval. When Liss occupies the interval [k - d, k + d] and a stone falls to k, she will escape to the left or to the right. If she escapes to the left, her new interval will be [k - d, k]. If she escapes to the right, her new interval will be [k, k + d].
You are given a string s of length n. If the i-th character of s is "l" or "r", when the i-th stone falls Liss will escape to the left or to the right, respectively. Find the sequence of stones' numbers from left to right after all the n stones falls.
Input
The input consists of only one line. The only line contains the string s (1 ≤ |s| ≤ 106). Each character in s will be either "l" or "r".
Output
Output n lines — on the i-th line you should print the i-th stone's number from the left.
Example
Input
llrlr
Output
3
5
4
2
1
Input
rrlll
Output
1
2
5
4
3
Input
lrlrr
Output
2
4
5
3
1

解题心得：

1、刚开始看到这个题的时候挺蒙蔽的，第一想法就是使用暴力，但是毫无疑问的是暴力肯定会将精度丢失，即使骗数据过了也容易被Hack。其实这个题有很多的解法

2、先说思路，题意上面说的很明白，当向左的时候最左方的一个是第一个r的前一个，最左方的r的是第一个r出现的时候，可以画一个图了解一下。

3、做法很多，了解了思路之后很简单，直接贴代码：

DFS：

#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e6+10;
char a[maxn];
int n;
void dfs(int step)
{if(step == n)return;if(a[step] == 'l'){dfs(step+1);printf("%d ",step+1);}if(a[step] == 'r'){printf("%d ",step+1);dfs(step+1);}
}
int main()
{while(scanf("%s",a)!=EOF){n = strlen(a);dfs(0);}
}

#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e6+10;
char a[maxn];
int main()
{scanf("%s",a);int len = strlen(a);stack <int> s;for(int i=0; i<len; i++){if(a[i] == 'l')s.push(i+1);elseprintf("%d ",i+1);}while(!s.empty()){printf("%d ",s.top());s.pop();}return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int maxn = 1e6+10;
int k[maxn];
char s[maxn];
int main()
{scanf("%s",s);{int len = strlen(s);int start = 0,End = len - 1;for(int i=0 ;i<len ;i++){if(s[i] == 'l'){k[start] = i+1;start++;}if(s[i] == 'r'){k[End] = i+1;End--;}}for(int i=len-1;i>=0;i--)printf("%d ",k[i]);}
}