Wednesday, May 11, 2011

Equilibrium index

The equilibrium index of an array is an index j such that the sum of the elements before j is equal to the sum of elements after j. Find j.
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2 comments:

  1. What about the below C++ code? Does that count as a solution? It returns -1, if no such index exists (I have not tested it, though :))

    ====

    int equilibrium(const int *a, const int n)
    {
    int sumRight = 0;
    for (int i = 0; i < n; ++i) sumRight += a[i];

    int j, sumLeft = 0;
    for (j = 0; j < n; ++j) {
    if (sumLeft == sumRight) break;
    sumLeft += a[j];
    sumRight -= a[j];
    }

    return (j == n-1)?-1:j;
    }

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