Frequency array to keep track of how many of the given intervals an element lies in
int freq [ MAX_VAL ] ; for ( int i = 0 ; i < N ; i ++ ) { li = arr [ i ] [ 0 ] ; freq [ li ] = freq [ li ] + 1 ; ri = arr [ i ] [ 1 ] ; freq [ ri + 1 ] = freq [ ri + 1 ] - 1 ; if ( li < min ) min = li ; if ( ri > max ) max = ri ; }