Segment Tree Range Minimum Query.

int rangeMinQuery(int segTree[], int qlow, int qhigh, int low, int high, int pos) {
    if (qlow <= low && qhigh >= high)
        return segTree[pos];
    if (qlow > high || qhigh < low)
        return maxVal;
    int mid = (low + high) / 2;
    return min(rangeMinQuery(segTree, qlow, qhigh, low, mid, 2*pos+1),
               rangeMinQuery(segTree, qlow, qhigh, mid+1, high, 2*pos+2));
}

void constructTree(int input[], int segTree[], int low, int high, int pos) {
    if (low == high) {
        segTree[pos] = input[low];
        return;
    }
    int mid = (low + high) / 2;
    constructTree(input, segTree, low, mid, 2*pos+1);
    constructTree(input, segTree, mid+1, high, 2*pos+2);
    segTree[pos] = min(segTree[2*pos+1], segTree[2*pos+2]);
}