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来源：互联网发布：知乎评价章泽天长相编辑：程序博客网时间：2024/06/02 03:20

n个区间[li , ri]，最少删除多少个区间，使得任何三个区间都不两两相交。

#include <stdio.h>#include <string>#include <stdlib.h>#include <vector>#include <algorithm>struct  Line{int left , right , idx ;Line(){} ;Line(int left , int right , int idx){this->left = left ;this->right = right ;this->idx = idx ;}};Line lines[50008] ;bool withLeftfromLessToBig(Line first , Line second) {return first.left < second.left ;}bool withRightfromBigToLess(Line first , Line second) {return second.right < first.right ;}bool intersect(Line a , Line b , Line c){    return b.left <= a.right && c.left <= b.right && c.left <= a.right ;}void solve() {    int t , n  , l , r ;    scanf("%d" , &t) ;    while (t-- > 0) {        scanf("%d" , &n) ;        for(int i = 0 ; i < n ; i++){            scanf("%d%d" , &l , &r) ;            lines[i] = Line(l , r , i+1) ;        }        if(n <= 2){            puts("") ;            continue ;        }        std::vector<int> res;        std::sort(lines , lines + n  ,withLeftfromLessToBig) ;        Line g[3] ;        g[0] = lines[0] ;        g[1] = lines[1] ;        for(int i = 2 ; i < n ; i++){            g[2] = lines[i] ;            std::sort(g , g + 3 ,  withLeftfromLessToBig) ;            bool isIntersect = intersect(g[0] , g[1] , g[2]) ;            std::sort(g , g + 3 ,  withRightfromBigToLess) ;            if(isIntersect){                res.push_back(g[0].idx) ;                g[0] = g[2] ;            }        }        std::sort(res.begin() , res.end()) ;        if(! res.empty()){            int size = res.size() ;            printf("%d\n" , size) ;            printf("%d" , res[0]) ;            for(int i = 1 ; i < size ; i++){                printf(" %d" , res[i]) ;            }        }        puts("") ;    }}int main(){    solve() ;    return 0;}

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