Ural 1019 Line Painting

点击打开链接ural 1019

思路：离散化
分析：
1 这一题的区间的最大值为10^9而n最大为5000，很明显就是利用离散化
2 题目中说了区间[0,10^9]刚开始为白色，而给定重刷的区间的值是大于0小于10^9的，所以我们应该开始就要考虑到0和10^9.
3 然后我们应该注意这题是对线段染色，所以我们应该要注意在处理的时候应该要把这些区间看成点来处理，然后会有两种方法分别是暴力和线段树

代码

线段树

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>using namespace std;const int MAXN = 10010;struct Node{    int left;    int right;    int mark;    char color;};Node node[4*MAXN] , tmp[MAXN];int n , pos;int num[MAXN];//二分查找int search(int x){    int left , right;    left = 1 , right = pos-1;    while(left <= right){        int mid = (left + right)>>1;        if(num[mid] == x)           return mid;        else if(num[mid] > x)           right = mid-1;        else           left = mid+1;    }}//建立线段树void buildTree(int left , int right , int pos){    node[pos].left = left;    node[pos].right = right;    node[pos].mark = 0;    if(left == right)      return;    int mid = (left+right)>>1;    buildTree(left , mid , pos<<1);    buildTree(mid+1 , right , (pos<<1)+1); }//向下更新void push_down(int pos){    if(node[pos].mark != -1){       node[pos<<1].mark = node[(pos<<1)+1].mark = node[pos].mark;       node[pos].mark = -1;    }}//更新void update(int left , int right , int value , int pos){    if(left <= node[pos].left && right >= node[pos].right){       node[pos].mark = value;       return;    }    push_down(pos);    int mid = (node[pos].left + node[pos].right)>>1;    if(right <= mid)      update(left , right , value , pos<<1);    else if(left > mid)      update(left , right , value , (pos<<1)+1);    else{      update(left , mid , value , pos<<1);       update(mid+1 , right , value , (pos<<1)+1);    }}//询问int query(int index , int pos){    if(node[pos].left == node[pos].right)       return node[pos].mark;    push_down(pos);    int mid = (node[pos].left + node[pos].right)>>1;    if(index <= mid)       return query(index , pos<<1);    else       return query(index , (pos<<1)+1);}int main(){    while(scanf("%d" , &n) != EOF){        pos = 1;        num[pos++] = 0;        num[pos++] = 1e9;        for(int i = 0 ; i < n ; i++){           scanf("%d %d %c" , &tmp[i].left , &tmp[i].right , &tmp[i].color);           num[pos++] = tmp[i].left;           num[pos++] = tmp[i].right;        }        sort(num+1 , num+pos);        pos = unique(num+1 , num+pos)-num;        //离散化        for(int i = 0 ; i < n ; i++){           tmp[i].left = search(tmp[i].left);           tmp[i].right = search(tmp[i].right);        }        buildTree(1 , pos-1 , 1);        //更新        for(int i = 0 ; i < n ; i++){           int value = 0;           if(tmp[i].color == 'b')              value = 1;           update(tmp[i].left , tmp[i].right-1 , value , 1);        }        //求解最长的白色区间        int left , right;        left = right = 0;        for(int i = 1 ; i < pos-1 ; i++){           if(!query(i , 1)){              int j = i+1;              while(j < pos-1 && !query(j , 1))                   j++;              int dis = num[j]-num[i];              if(dis > right-left){                 left = num[i];                 right = num[j];              }              i = j;           }        }        printf("%d %d\n" , left , right);    }    return 0;}

暴力

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm>using namespace std;const int MAXN = 100010;struct Node{    int left;    int right;    int mark;    char color;};Node node[MAXN];int vis[MAXN];int num[MAXN];int pos;//二分查找int search(int x){    int left = 1 , right = pos-1;    while(left <= right){        int mid = (left+right)>>1;         if(num[mid] == x)          return mid;        else if(num[mid] > x)          right = mid-1;        else          left = mid+1;    }}int main(){    int n;    while(scanf("%d" , &n) != EOF){        pos = 1;        num[pos++] = 0;        num[pos++] = 1e9;        for(int i = 0 ; i < n ; i++){            scanf("%d %d %c" , &node[i].left , &node[i].right , &node[i].color);            num[pos++] = node[i].left;            num[pos++] = node[i].right;        }        sort(num+1 , num+pos);        pos = unique(num+1 , num+pos)-num;        for(int i = 0 ; i < n ; i++){           node[i].left = search(node[i].left);           node[i].right = search(node[i].right);        }        //染色        memset(vis , 0 , sizeof(vis));        for(int i = 0 ; i < n ; i++){            int value = 0;            if(node[i].color == 'b')              value = 1;            for(int j = node[i].left ; j < node[i].right ; j++)              vis[j] = value;        }        int left , right;        left = right = 0;        //找最大的连续的白色区间        for(int i = 1 ; i < pos-1 ; i++){           if(!vis[i]){             int j = i+1;             while(j < pos-1 && !vis[j])                  j++;             int dis = num[j]-num[i];             if(dis > right-left){                right = num[j];                left = num[i];             }             i = j;           }        }        printf("%d %d\n" , left , right);    }    return 0;}