选择题：In one year rats eat 40 to 50 times ___ weight. A.its B.and C.their D.theirs

Posted 2023-05-09

选C,缺少物主代词，所以在A和C中选择，而A表示单数，前面是rats，为复数，用their；若前面是a
rat或the
rat
则选A 参考技术A C
是rats，所以后面也要用复数。
their
是“他们的”，而
theirs
则是“他们的东西”。这里后面有weight，所以只能用
their。

c_cpp iNautix Rat in a Maze - Diamonds

#include<bits/stdc++.h>
using namespace std;

// iNautix
// #Placement
// 0 path, 1 diamond, -1 block
// possible movements right, down
// reverse up, left

int maxD(vector< vector <int> > a);
bool valid(vector< vector<int> > a, int x, int y);
bool btFWD(vector < vector<int> > a, int x, int y);
int solveFWD(vector< vector<int> > &a, int r,int c,int x,int y, int di);
bool btREV(vector < vector<int> > a, int x, int y);
int solveREV(vector< vector<int> > &a, int r,int c,int x,int y, int di);

int main(){
    int t;
    cin>>t;
    while(t--){
        int r,c;
        cin>>r>>c;
        vector< vector<int> > a(r);
        for(int i=0;i<r;i++){
            for(int j=0;j<c;j++){
                int x;
                cin>>x;
                a[i].push_back(x);
            }
        }
        cout<<maxD(a)<<endl;
    }
    return 0;
}

int maxD(vector< vector <int> > a){
    int r=a.size();
    int c=a[0].size();
    int fwd=solveFWD(a,r,c,0,0,0);
    int ans=solveREV(a,r,c,r-1,c-1,fwd);
    return ans;
}
bool valid(vector< vector<int> > a, int x, int y){
    int r=a.size();
    int c=a[0].size();
    if(x<0 || y<0 || x>=r || y>=c){
        return false;
    }
    if(a[x][y]==-1){
        return false;
    }
    return true;
}
bool btFWD(vector < vector<int> > a, int x, int y){
    int r=a.size();
    int c=a[0].size();
    if(x==r-1 && y==c-1){
        return true;
    }
    if(valid(a,x,y)==true){
        if(btFWD(a,x,y+1)==true){
            return true;
        }
        if(btFWD(a,x+1,y)==true){
            return true;
        }
        return false;
    }
    return false;
}
int solveFWD(vector< vector<int> > &a, int r,int c,int x,int y, int di){
    if(x==r-1 && y==c-1){
        di+=a[x][y];
        a[x][y]=0;
        return di;
    }
    if(btFWD(a,x,y)==true){
        di+=a[x][y];
        a[x][y]=0;
        vector< vector<int> > aCPY=a;
        int right=solveFWD(a,r,c,x,y+1,di);
        int down=solveFWD(aCPY,r,c,x+1,y,di);
        if(right<down){
        	a=aCPY;	// IMP step
        	return down; // make a copy of array to backtrack
        }else{
        	return right;
        }
    }else{
        return -1; // No Path
    }
}
bool btREV(vector < vector<int> > a, int x, int y){
    if(x==0 && y==0){
        return true;
    }
    if(valid(a,x,y)==true){
        if(btREV(a,x,y-1)==true){
            return true;
        }
        if(btREV(a,x-1,y)==true){
            return true;
        }
        return false;
    }
    return false;
}
int solveREV(vector< vector<int> > &a, int r,int c,int x,int y, int di){
    if(x==0 && y==0){
    	di+=a[x][y];
        a[x][y]=0;
        return di;
    }
    if(btREV(a,x,y)==true){
        di+=a[x][y];
        a[x][y]=0;
        vector< vector<int> > aCPY=a;
        int left=solveREV(a,r,c,x,y-1,di);
        int up=solveREV(aCPY,r,c,x-1,y,di);
        if(left<up){
        	a=aCPY;
        	return up;
        }else{
        	return left;
        }
    }else{
        return -1; // No Path
    }
}