[improvement class] st table to solve the interval maximum value problem [2]

【 Improvement course 】ST Table solves the interval maximum problem
This was written before , Now rearrange the template , The subscript of the minimum value can be returned .

ST Table calculation of interval minimum value ：

struct st_pair{
    
    int w, idx;
    bool operator < (const st_pair & x) const{
    
        return w < x.w;
    }
};

st_pair f[N][LG];

void init(){
    
    rep(j, 0, LG - 1){
    
        for(int i = 1; i + (1 << j) - 1 <= n; i ++ ){
    
            if(!j) f[i][j] = {
    a[i], i};
            else f[i][j] = min(f[i][j - 1], f[i + (1 << j - 1)][j - 1]);
        }
    }
}

st_pair query(int l, int r){
    
    int k = __lg(r - l + 1);
    return min(f[l][k], f[r - (1 << k) + 1][k]);
}