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    boolean[] vis;
    int[] ans;
    int pointer;
    void addEdge(int a, int b) {
        ans[pointer++] = a;
        ans[pointer++] = b;
    }
    public int[] findAnyGraph(int n, int m, int k) {
        int need = 1;
        for(int i = 0; i < k; ++i) {
            need *= 2;
            if(need > n) {
                int[] nothing = new int[1];
                nothing[0] = -1;
                return nothing;
            }
        }
        ans = new int[2*m];
        pointer = 0;
        int power_of_two = 1;
        for(int rep = 0; rep < k; ++rep) {
            for(int i = power_of_two; i <= need-1; i += 2*power_of_two)
                addEdge(i, i+1);
            power_of_two *= 2;
        }
        for(int i = 1; i <= n; ++i)
            for(int j = n; j >= i+1; --j)
                if(j > need || j > i+1)
                if(pointer < 2 * m)
                    addEdge(i, j);
        return ans;
    }
 

prog.cpp:1:5: error: 'boolean' does not name a type
     boolean[] vis;
     ^
prog.cpp:2:8: error: expected unqualified-id before '[' token
     int[] ans;
        ^
prog.cpp: In function 'void addEdge(int, int)':
prog.cpp:5:9: error: 'ans' was not declared in this scope
         ans[pointer++] = a;
         ^
prog.cpp: At global scope:
prog.cpp:8:5: error: expected unqualified-id before 'public'
     public int[] findAnyGraph(int n, int m, int k) {
     ^

Standard output is empty